Liquid crystals

ABSTRACT

Compounds of the formula ##STR1## wherein R 1  is hydrogen or straight-chain alkyl; R 2  is --CN, --R, --COR, --COOR or when R 2  is positioned on an aromatic ring R 2  also can be --OR, --OOCR or --F; R is alkyl; A is a group with 1 to 4 six-membered rings, these rings being linked directly with one another and with ring B in each case via a single covalent bond or being linked at one or two positions also via --COO--, --OOC-- or --CH 2  CH 2  --; the six-membered rings in A and ring B each are 1,4-phenylene or trans-1,4-cyclohexylene or one of these rings also is trans-2,5-disubstituted m-dioxane, 2,5-disubstituted pyrimidine or 3,6-disubstituted pyridazine, with the proviso that a maximum of two adjacent trans-1,4-cyclohexylene rings are linked directly via a single covalent bond; and m is the integer 2, or when ring B is trans-1,4-cyclohexylene or trans-2,5-disubstituted m-dioxane, m also can be the integer 0, their manufacture, liquid crystalline mixtures which contain these compounds as well as the use of these compounds for electro-optical purposes are described. 
     Additionally, compounds of the formula ##STR2## wherein R 8  is straight-chain C 1  -C 12  alkyl, their manufacture, liquid crystalline mixtures which contain these compounds and their use for electro-optical purposes are described.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to liquid crystalline compounds and mixtures.

2. Description

Liquid crystals have recently gained considerably importance primarilyas dielectrics in indicating devices, since the optical properties ofsuch substances can be influenced by an applied voltage. Electro-opticaldevices based on liquid crystals are well known to the person skilled inthe art and can be based on various effects such as, for example,dynamic scattering, the deformation of aligned phases (DAP type), theSchadt-Helfrich effect (rotation cell), the guest/host effect or acholesteric-nematic phase transition (phase change effect).

Liquid crystals must satisfy a number of requirements in order to besuitable as dielectrics for electro-optical indicating devices. Forexample, they must have a good chemical stability towards environmentalfactors such as, for example, heat, moisture, air and electromagneticradiation in the infrared, visible and ultraviolet range. Further, theyshould be colourless, should have short response times and should havenot too high a viscosity, should give a good contrast and should have anematic or cholesteric mesophase in the entire temperature range inwhich the liquid crystal cell is to be operated. Other properties mustfulfil different conditions depending on the type of cell which is used;for example, liquid crystals which are used in rotation cells shouldhave a large positive anisotropy of the dielectric constants (Δε=ε.sub.∥-ε.sub.⊥ >0, ε.sub.∥ signifying the dielectric constant along thelongitudinal molecular axis and ε.sub.⊥ signifying the dielectricconstant perpendicular thereto) and liquid crystals which are used inguest/host cells should have a large positive or negative anisotropy ofthe dielectric constants. Moreover, in both cases a low thresholdpotential and a conductivity which is as small as possible aredesirable.

Since, in general, it is not possible to achieve all desired and to someextent contradictory properties with a single compound, attempts havemainly been made to optimize the properties for the particularapplications by mixing several components. In this case it is, however,important that the components undergo no chemical reactions with oneanother and have a good miscibility. Further, the mixtures formed shouldhave no smectic mesophases, at least at temperatures at which the liquidcrystal cell is to be operated.

There are already known a number of liquid crystalline compounds anddoping agents for liquid crystal mixtures which have as wing groups, forexample, alkyl, alkoxy, alkanoyloxy, alkoxycarbonyl and cyano groups.

SUMMARY OF THE INVENTION

The invention is concerned with liquid crystal compounds of the formula##STR3## wherein R¹ signifies hydrogen or straight-chain alkyl; R²represents --CN, --R, --COR, --COOR or on an aromatic ring also --OR,--OOCR or fluorine and R denotes alkyl; A stands for a group with 1 to 4six-membered rings, these rings being linked directly with one anotherand with ring B in each case via a single covalent bond or being linkedat one or optionally two positions also via --COO--, --OOC-- or --CH₂CH₂ --; the six-membered rings in A and ring B signify 1,4-phenylene ortrans-1,4-cyclohexylene or one of these rings also signifies atrans-2,5-disubstituted m-dioxane ring, a 2,5-disubstituted pyrimidinering or a 3,6-disubstituted pyridazine ring, and a maximum of twoadjacent trans-1,4-cyclohexylene rings are linked directly via a singlecovalent bond; and m denotes the number 2 or, insofar as ring Bsignifies trans-1,4-cyclohexylene or a trans-2,5-disubstituted m-dioxanering, also the number 0.

It has now been found that the above compounds provided by the inventionhave a satisfactory stability towards electromagnetic radiation and thatthe trans-1-alkenyl or trans-3-alkenyl side-chain exerts a favourableinfluence on the mesophase behaviour. Further, the compounds provided bythe invention have a good miscibility with known liquid crystals andalso have the remaining requisite properties referred to above.Depending on the significance of ring B and of groups A and R² thecompounds provided by the invention cover a broad spectrum of the widestvariety of electro-optical applications. For example, the compoundswhich contain a pyrimidine ring and/or a cyano group have a positiveanisotropy of the dielectric constants (Δε=ε.sub.∥ -ε.sub.⊥ >0, ε.sub.∥signifying the dielectric constant along the longitudinal molecular axisand ε.sub.⊥ signifying the dielectric constant perpendicular thereto),while a pyridazine ring confers a negative dielectric anisotropy to thecompounds. On the other hand, the compounds which contain no cyano groupand no pyrimidine or pyridazine ring have a low viscosity and a smallabsolute sum of the dielectric anisotropies. The compounds which containa m-dioxane ring are primarily of interest for producing low thresholdpotentials and short response times. The compounds provided by theinvention are for the most part themselves liquid crystalline and someof them have a very large mesophase range. Those compounds provided bythe invention which have only monotropic or virtual clearing points suchas, for example, the compounds of formula I in which A signifies1,4-phenylene or a 3,6-disubstituted pyridazine ring, ring B signifiestrans-1,4-cyclohexylene and R² signifies alkyl or alkoxy are primarilysuitable as doping agents for liquid crystal mixtures. The presentinvention therefore extends considerably the choice of suitable liquidcrystal components which, in particular, facilitates the furtheroptimization of mixtures.

The invention is also concerned with the manufacture of the compounds offormula I above, liquid crystalline mixtures which contain compounds offormula I above as well as the use of compounds of formula I above forelectro-optical purposes.

The invention is also concerned with liquid crystal compounds of theformula ##STR4## wherein R⁸ is straight-chain C₁ -C₁₂ -alkyl, as well asthe manufacture of the compounds of formula LXXVIII above, liquidcrystalline mixtures which contain these compounds and their use forelectro-optical purposes.

The compounds of formula LXXVIII have at the same time a large positiveanisotropy of the dielectric constants, a small optical anisotropy, lowviscosity (especially when used in mixtures), low threshold potentialsand short response times as well as an improved mesophase behaviour.Further, they have a high chemical stability and only slightconductivity, they are colourless and have a good miscibility with allcustomary liquid crystals and give a high contrast in indicatingdevices. The compounds provided by the invention are therefore very wellsuited for liquid crystalline dielectrics in electro-optical indicatingdevices such as, for example, in rotation cells and guest/host cells,especially in rotation cells.

DETAILED DESCRIPTION OF THE INVENTION

As used herein the terms "alkyl" and "C₁ -C₁₂ alkyl" denotestraight-chain alkyl groups of 1 to 12 carbon atoms (e.g., methyl,ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl,undecyl, dodecyl and the like) as well as branched-chain alkyl groups of1 to 12 carbon atoms, especially 1-methylalkyl and 2-methylalkyl (e.g.,isopropyl, isobutyl, sec.butyl, 1-methylbutyl, 2-methylbutyl,1-methylpentyl, 2-methylpentyl, 1-methylhexyl, 2-methylhexyl and thelike).

The terms "straight-chain alkyl" and "C₁ -C₁₂ straight-chain alkyl"denote straight-chain alkyl groups of 1 to 12 carbon atoms.

The terms "alkoxy" and "alkoxycarbonyl", as well as any other groups inthe specification containing "alkyl", denotes moieties in which their"alkyl" portions are as defined previously.

The term "alkanoyloxy" denotes moieties derived from alkanecarboxylicacid moieties of 2 to 13 carbon atoms.

The term "halogen" denotes chlorine, bromine or iodine.

Ring B is 1,4-phenylene, trans-1,4-cyclohexylene, atrans-2,5-disubstituted m-dioxane ring, a 2,5-disubstituted pyrimidinering or a 3,6-disubstituted pyridazine ring. Group A contains 1 to 4six-membered rings. The rings in group A can signify 1,4-phenyleneand/or trans-1,4-cyclohexylene. When ring B stands for 1,4-phenylene ortrans-1,4-cyclohexylene, one of the rings in group A can also signify atrans-2,5-disubstituted m-dioxane ring, a 2,5-disubstituted pyrimidinering or a 3,6-disubstituted pyridazine ring. Eachtrans-1,4-cyclohexylene ring which may be present in formula I can belinked directly with at most one further trans-1,4-cyclohexylene ringvia a single covalent bond.

The term "aromatic ring" used herein denotes a benzene, pyrimidine orpyridazine ring. The term "heterocyclic ring" denotes in the scope ofthe present invention a pyrimidine, pyridazine or m-dioxane ring.

The invention is concerned with novel liquid crystal componentscontaining a trans-1-alkenyl or a trans-3-alkenyl side-chain, namelycompounds of the general formula ##STR5## wherein R¹ is hydrogen orstraight-chain alkyl; R² is --CN, --R, --COR, --COOR or when R² ispositioned on an aromatic ring R² also can be --OR, --OOCR or --F; R isalkyl; A is a group with 1 to 4 six-membered rings, these rings beinglinked directly with one another and with ring B in each case via asingle covalent bond or being linked at one or two positions also via--COO--, --OOC-- or --CH₂ CH₂ --; the six-membered rings in A and ring Beach are 1,4-phenylene or trans-1,4-cyclohexylene or one of these ringsalso is trans-2,5-disubstituted m-dioxane, 2,5-disubstituted pyrimidineor 3,6-disubstituted pyridazine, with the proviso that a maximum of twoadjacent trans-1,4-cyclohexylene rings are linked directly via a singlecovalent bond; and m is the integer 2, or when ring B istrans-1,4-cyclohexylene or trans-2,5-disubstituted m-dioxane, m also canbe the integer 0.

A preferred group of compounds within formula I having the formula##STR6## wherein each of rings B¹, B², B³ and B⁴ is 1,4-phenylene ortrans-1,4-cyclohexylene; n is the integer 0 or 1; each of X¹, X², X³ andX⁴ is a single covalent bond or one or two of these symbols also is--COO--, --OOC-- or --CH₂ CH₂ --, with the proviso that a maximum of twoadjacent trans-1,4-cyclohexylene rings are linked directly via a singlecovalent bond; and R¹, R², R and m have the significances given above.

Preferably, m in formula V stands for the number 0. Especially preferredcompounds of formula V are those in which X¹ denotes a single covalentbond, --COO-- or --CH₂ CH₂ --, the symbols X², X³ and X⁴ representsingle covalent bonds, the rings B¹, B² and B³ stand for 1,4-phenyleneand R² signifies cyano, alkyl or on an aromatic ring also alkoxy.Further, ring B⁴ preferably stands for trans-1,4-cyclohexylene when R²signifies alkyl and ring B⁴ preferably stands for 1,4-phenylene when R²signifies cyano.

However, in general, the bicyclic and the tricyclic compounds, (i.e. thecompounds of formula I in which group A has one or two six-memberedrings), stand in the foreground of interest. Preferred compoundsprovided by the invention are therefore the compounds of the formula##STR7## wherein rings B, C and D each are 1,4-phenylene,trans-1,4-cyclohexylene or one of these rings also can betrans-2,5-disubstituted m-dioxane, 2,5-disubstituted pyrimidine or3,6-disubstituted pyridazine; one of X¹ and X² is a single covalent bondand the other is --COO--, --OOC--, --CH₂ CH₂ --, or when at least one ofthe rings B, C and D is not trans-1,4-cyclohexylene, the other of X¹ andX² also can be a single covalent bond; n is the integer 0 or 1; and R¹,R², R and m have the significances given above.

Ring B in formulae I and Ia preferably stands fortrans-1,4-cyclohexylene or a trans-2,5-disubstituted m-dioxane ring.Further, in formula Ia n preferably stands for the number 0. In general,m preferably stands for the number 0 when ring B signifiestrans-1,4-cyclohexylene or a trans-2,5-disubstituted m-dioxane ring.

Preferred compounds falling under formulae I and Ia are the compounds ofthe formula ##STR8## wherein each of rings B¹ and B² is 1,4-phenylene ortrans-1,4-cyclohexylene; one of X¹ and X² is a single covalent bond andthe other is --COO--, --OOC--, --CH₂ CH₂ --, or when at least one of therings B¹ and B² is not trans-1,4-cyclohexylene, the other of X¹ and X²also can be a single covalent bond; n is the integer 0 or 1; and R¹, R²,R and m have the significances given above, the compounds of the formula##STR9## wherein ring E is 2,5-disubstituted pyrimidine; ring B¹ is1,4-phenylene or trans-1,4-cyclohexylene; X¹ is a single covalent bond,--COO--, --OOC-- or --CH₂ CH₂ --; n is the integer 0 or 1; and R¹, R²,and m have the significances given above, the compounds of the formula##STR10## wherein ring B¹ is 1,4-phenylene or trans-1,4-cyclohexylene;each of X¹ and X² is a single covalent bond or one of X¹ and X² also is--COO--, --OOC-- or --CH₂ CH₂ --; n is the integer 0 or 1; R³ is --R,--COR, --COOR, or when R³ is positioned on an aromatic ring R³ also canbe --OR or --OOCR; and R¹, R and m have the significances given above,and the compounds of the formula ##STR11## wherein each of rings B¹ andB² is 1,4-phenylene or trans-1,4-cyclohexylene; n is the integer 0 or 1;and R¹, R², R and m have the significances given above.

Especially preferred compounds of formula II are those in which X¹denotes a single covalent bond, --COO--, --OOC-- or --CH₂ CH₂ -- and X²denotes a single, covalent bond, rings B¹ and B² represent 1,4-phenyleneand R² signifies cyano, alkyl or alkoxy. Further, in formula II npreferably signifies the number 0 and/or X¹ preferably signifies asingle covalent bond.

Especially preferred compounds of formula III are those in which X¹ ispresent in the 5-position of the pyrimidine ring E and denotes a singlecovalent bond. Preferred groups denoted by R² are alkyl, alkoxy andespecially cyano. Preferably, n stands for the number 1 and ring B¹stands for 1,4-phenylene.

Especially preferred compounds of formula IV are those in which X¹ andX² denote single covalent bonds or one of these symbols also denotes--CH₂ CH₂ -- and R³ signifies alkyl or on an aromatic ring also alkoxy,particularly those compounds in which X¹ denotes a single covalent bondand n denotes the number 0.

Especially preferred compounds of formula Ib are those in which ndenotes the number 0 and R² denotes cyano, alkyl or on an aromatic ringalso alkoxy. Ring B¹ preferably stands for 1,4-phenylene.

The group R in the above definitions of R² and R³ is conveniently analkyl group containing 1 to 12 carbon atoms, especially a straight-chainalkyl group containing 1 to 12 carbon atoms.

Further, there are, in principle, preferred those compounds of formula Iin which R² signifies cyano, alkyl or on an aromatic ring also alkoxy.Preferred alkyl and alkanoyl groups R² or R³ are those containing 3 to 7carbon atoms and preferred alkoxy, alkanoyloxy and alkoxycarbonyl groupsR² or R³ are those containing 2 to 6 carbon atoms.

The symbol R¹ in formulae I, Ia, Ib, II, III, IV and V above preferablysignifies hydrogen or straight-chain C₁ -C₁₀ -alkyl, especially hydrogenor straight-chain C₁ -C₅ -alkyl, when m stands for the number 0, andpreferably signifies hydrogen or straight-chain C₁ -C₈ -alkyl,especially hydrogen or straight-chain C₁ -C₃ -alkyl, when m stands forthe number 2. In the scope of the present invention the term"trans-1-alkenyl" therefore embraces in particular the groups vinyl,trans-1-propenyl, trans-1-butenyl, trans-1-pentenyl, trans-1-hexenyl,trans-1-heptenyl, trans-1-octenyl, trans-1-nonenyl, trans-1-decenyl,trans-1-undecenyl and trans-1-dodecenyl and the term "trans-3-alkenyl"embraces in particular the groups 3-butenyl, trans-3-pentenyl,trans-3-hexenyl, trans-3-heptenyl, trans-3-octenyl, trans-3-nonenyl,trans-3-decenyl, trans-3-undecenyl and trans-3-dodecenyl.

Further preferred groups of compounds provided by the invention andexamples of preferred compounds are the compounds falling under formulaI which are mentioned in the Reaction Schemes and the Exampleshereinafter.

The compounds of formula I can be manufactured in accordance with theinvention by the following procedure:

(a) for the manufacture of the compounds of formula I in which R¹signifies primary alkyl containing at least 2 carbon atoms, R²represents --CN, --R or on an aromatic ring also --OR or fluorine andthe rings present in A are linked directly with one another and withring B in each case via a single covalent bond or are linked at one oroptionally two positions also via --CH₂ CH₂ --, reacting a compound ofthe formula ##STR12## wherein Y¹ denotes a leaving group; R⁴ represents--CN, --R or on an aromatic ring also --OR or fluorine and R signifiesalkyl; A¹ stands for a group with 1 to 4 six-membered rings, these ringsbeing linked directly with one another and with ring B in each case viaa single covalent bond or being linked at one or optionally twopositions also via --CH₂ --CH₂ --; the six-membered rings in A and ringB signify 1,4-phenylene or trans-1,4-cyclohexylene or one of these ringsalso signifies a trans-2,5-disubstituted m-dioxane ring, a2,5-disubstituted pyrimidine ring or a 3,6-disubstituted pyridazinering, and a maximum of two adjacent trans-1,4-cyclohexylene rings arelinked directly via a single covalent bond; and m denotes the number 2or, insofar as ring B signifies trans-1,4-cyclohexylene or atrans-2,5-disubstituted m-dioxane ring, also the number 0, with analkylmagnesium halide in the presence of dilithium tetrachlorocuprate ordilithium tetrabromocuprate, or

(b) for the manufacture of the compounds of formula I in which R¹signifies methyl, R² represents --CN, --R or on an aromatic ring also--OR or fluorine and the rings present in A are linked directly with oneanother and with ring B in each case via a single covalent bond or arelinked at one or optionally two positions also via --CH₂ CH₂ --,reducing a compound of formula VI, or

(c) for the manufacture of the compounds of formula I in which R²represents --COR and the rings present in A are linked directly with oneanother and with ring B in each case via a single covalent bond or arelinked at one or optionally two positions also via --CH₂ CH₂ --,reacting a compound of the formula ##STR13## wherein R¹ denotes hydrogenor straight-chain alkyl and A¹, m and ring B have the significancesgiven in formula VI, with an alkylmagnesium halide in the presence ofdilithium tetrachlorocuprate or dilithium tetrabromocuprate, or

(d) for the manufacture of the compounds of formula I in which Acontains at least one group --COO-- or --OOC-- and/or R² represents--COOR or --OOCR, esterifying a compound of the formula ##STR14## with acompound of the formula

    Y.sup.3 --A.sup.3 --R.sup.5                                IX

wherein R¹ signifies hydrogen or straight-chain alkyl; one of thesymbols Y² and Y³ represents --COOH or --COCl and the other represents--OH; A² and A³ each stand for a group with 1 to 4 six-membered rings orone of the groups A² and A³ can also be absent, with the proviso that A²and A³ together contain a maximum of 4 rings; ring B is linked directlyvia a single covalent bond optionally with six-membered rings present inA² and, insofar as A² and/or A³ have several six-membered rings, theserings are linked directly with one another in each case via a singlecovalent bond or one or, insofar as A³ is absent, optionally also two ofthese linkages are effected via --COO--, --OOC-- or --CH₂ CH₂ --; thesix-membered rings in A² and A³ and ring B signify 1,4-phenylene ortrans-1,4-cyclohexylene or one of these rings also signifies atrans-2,5-disubstituted m-dioxane ring, a 2,5-disubstituted pyrimidinering or a 3,6-disubstituted pyridazine ring, and a maximum of twoadjacent trans-1,4-cyclohexylene rings are linked directly via a singlecovalent bond; m denotes the number 2 or, insofar as ring B signifiestrans-1,4-cyclohexylene or a trans-2,5-disubstituted m-dioxane ring,also the number 0; and R⁵ represents --CN, --R, --COR, --COOR or on anaromatic ring also --OR, --OOCR or fluorine when A³ stands for a groupwith 1 to 4 six-membered rings or R⁵ represents --R when A³ is absentand R denotes alkyl, or

(e) for the manufacture of the compounds of formula I in which R²represents --CN, --R or on an aromatic ring also --OR or fluorine andthe rings present in A are linked directly with one another and withring B in each case via a single covalent bond or are linked at one oroptionally two positions also via --CH₂ CH₂ --, reacting a compound ofthe formula ##STR15## wherein A¹, R⁴, m and ring B have thesignificances given in formula VI, with an alkyltriphenylphosphoniumhalide in the presence of a base, or

(f) for the manufacture of the compounds of formula I in which ring B orone of the six-membered rings in A signifies a trans-2,5-disubstitutedm-dioxane ring, reacting a compound of the formula ##STR16## with acompound of the formula

    Y.sup.5 --A.sup.5 --R.sup.2                                XXXVI

wherein R¹ signifies hydrogen or straight-chain alkyl; R² represents--CN, --R, --COR, --COOR or on an aromatic ring also --OR, --OOCR orfluorine and R denotes alkyl; one of the symbols Y⁴ and Y⁵ signifies--CH(CH₂ OH)₂ and the other signifies --CHO or an acetal group; A⁴ andA⁵ each stand for a group with 1 to 4 1,4-phenylene ortrans-1,4-cyclohexylene rings or one of the groups A⁴ and A⁵ can also beabsent, with the proviso that A⁴ and A⁵ together contain a maximum of 4rings; Y⁴ and Y⁵ are linked directly via a single covalent bondoptionally with six-membered rings present in A⁴ or in A⁵ and, insofaras A⁴ and/or A⁵ have several six-membered rings, these rings are linkeddirectly with one another in each case via a single covalent bond or oneor two of these linkages are effected via --COO--, --OOC-- or --CH₂ CH₂--; a maximum of two adjacent trans-1,4-cyclohexylene rings are linkeddirectly via a single covalent bond; and m signifies the number 2 or,when A⁴ is absent or the group R¹ --CH═CH--(CH₂)_(m) -- stands on atrans-1,4-cyclohexylene ring, also the number 0.

The reaction of a compound of formula VI with an alkylmagnesium halide(process variant a) can be carried out in a manner known per se. Theterm "halide" used in this connection stands for chloride, bromide oriodide, preferably for bromide. Dilithium tetrachlorocuprate is thepreferred catalyst. Y¹ signifies any leaving group which is usual insuch reactions, for example alkanoyloxy, alkylsulphonyloxy,arylsulphonyloxy or halogen such as acetoxy, methanesulphonyloxy,benzenesulphonyloxy, tosyloxy, naphthalenesulphonyloxy, bromine, iodineand the like. The reaction is conveniently carried out in an ether suchas dimethoxyethane, diethylene glycol dimethyl ether, tetrahydrofuran,dioxan, diethyl ether and the like. The solvent is preferablytetrahydrofuran or a mixture of tetrahydrofuran and diethyl ether. Thetemperature and pressure can be held in wide limits. However, thereaction is generally carried out at atmospheric pressure and at atemperature between about -80° C. and room temperature. The reaction ispreferably carried out at a temperature of below about 0° C. andespecially at about -15° C.

The reduction of a compound of formula VI in accordance with processvariant (b) can be carried out accordingly to methods known per se; forexample, by reacting a compound of formula VI in which Y¹ signifiesiodine with triphenylphosphonium iodide and by reacting a compound offormula VI in which Y¹ signifies acetoxy with methanolic potassiumhydroxide solution and triphenylphosphine-iodine. Such reactions aredescribed, for example, in Chem. Ber. 109, 1586 (1976).

The reaction of a compound of formula VII with an alkylmagnesium halide(process variant (c)) can be carried out in an analogous manner toprocess variant (a). However, it is generally carried out at a somewhathigher temperature, preferably at about 0° C. to the reflux temperatureof the reaction mixture.

The esterification of a compound of formula VIII with a compound offormula IX (process variant (d)) can be carried out in a manner knownper se. The esterification of the acid chlorides (which can be obtainedfrom the carboxylic acids, for example by heating with thionyl chloride)can be carried out, for example, in diethyl ether, tetrahydrofuran,dimethylformamide, benzene, toluene, carbon tetrachloride, pyridine andthe like. The esterification of a carboxylic acid is preferably carriedout in the presence of 4-(dimethylamino)pyridine andN,N'-dicyclohexylcarbodiimide or in the presence of oxalyl chloride anddimethylformamide. The temperature and pressure at which theseesterifications are carried out are not critical and there are generallyused atmospheric pressure and a temperature between about -30° C. andthe boiling point of the reaction mixture.

The reaction of a compound of formula X with analkyltriphenylphosphonium halide in the presence of a base (e.g.potassium carbonate) (process variant (e)) can also be carried out in amanner known per se. The term "halide" used in this connection standsfor chloride, bromide or iodide, preferably for bromide. The reaction isconveniently carried out in an inert organic solvent, for example anether such as diethyl ether, tetrahydrofuran, dioxan and the like. Thetemperature and pressure are not critical, although the reaction isgenerally carried out at atmospheric pressure and at a temperature ofroom temperature up to the reflux temperature of the reaction mixture.

The reaction of a compound of formula XXXV with a compound of formulaXXXVI (process variant (f)) can be carried out in a manner known per se.The reaction of the diol with the aldehyde or a suitable acetal thereof(e.g. the dimethyl acetal) is conveniently carried out in an inertorganic solvent in the presence of a catalytic amount of an organic orinorganic acid. Hydrocarbons, especially aromatic hydrocarbons such asbenzene, toluene, xylene and the like, are preferred solvents. Dryhydrogen chloride and sulphonic acids, especially p-toluenesulphonicacid, are preferred acids. The temperature and pressure are notcritical, but the reaction is preferably carried out at the refluxtemperature of the reaction mixture and under atmospheric pressure. Thedioxanes are generally obtained as cis/trans mixtures, from which thepure trans compounds can be obtained readily by recrystallization. Ifdesired, the mother liquors can be converted with acid into thecis/trans equilibrium mixture which can again be subjected torecrystallization.

In the manufacture of compounds of formula I in which m signifies thenumber 0 and ring B signifies trans-1,4-cyclohexylene according toprocess variant (e) the cyclohexane ring is obtained almost exclusively(about 98%) in the trans-configuration; this also applies when acis/trans isomer mixture (a compound of formula X in which m signifiesthe number 0 and ring B signifies cis-1,4-cyclohexylene ortrans-1,4-cyclohexylene) is used as the starting material. This processtherefore also provides an excellent possibility for the manufacture ofcorresponding trans-4-alkylcyclohexyl compounds by subsequent catalytichydrogenation in a manner known per se (e.g. with palladium, platinum orRaney-nickel).

The compounds of formulae IX and XXXVI are known or can be prepared fromknown compounds by conventional techniques.

The compounds of formulae VI, VIII, X and XXXV are novel and arelikewise objects of the present invention. The manufacture of thecompounds of formula I and the preparation of the compounds of formulaeVI, VII, VIII, X and XXXV is illustrated on the basis of representativeexamples in Reaction Schemes 1-11 hereinafter in which R⁶ denotesstraight-chain alkyl, R⁷ denotes hydrogen or straight-chain alkyl, Tsdenotes p-tosyl and ring B¹ denotes 1,4-phenylene ortrans-1,4-cyclohexylene and R¹, R⁴ and R have the above significances.The starting materials which are required in these Reaction Schemes areknown or are analogues of known compounds. ##STR17##

If in place of the cyano compound of formula XI there is reacted inaccordance with Scheme 1 a corresponding alkyl, alkoxy or fluorocompound, then the penultimate step (XVI→XVII) can be omitted, sincealkyl, alkoxy and fluorine are not affected in the reduction withdiisobutylaluminium hydride. The introduction of other leaving groups Y¹(in place of the acetoxy group in formula XVII or analogous compounds)can be carried out according to methods known per se. Further examplesare given in Scheme 6.

In the manufacture of the compounds of formula IC and Ih in which R¹signifies straight-chain alkyl in accordance with Scheme 1 or 7 (processvariant (e)) there generally results a mixture consisting of cis-alkenylcompound and trans-alkenyl compound. Such mixtures can be separated bychromatography on silica gel coated with silver nitrate. If desired, thecis-alkenyl compounds (or mixtures containing predominantly cis-alkenylcompound) can be converted into the corresponding trans-alkenylcompounds in accordance with Scheme 6 or 7.

The reaction XXIII→Ie in accordance with Scheme 2 can be carried out inan analogous manner to Scheme 1.

The preparation of acids and alcohols of formula VIII and theintroduction of trans-3-alkenyl groups are illustrated in Schemes 3-5, 7and 8. Additional acids of formula VIII can also be obtained bysaponifying nitriles of formula VII.

The manufacture of compounds of formula I in which one of the ringssignifies a dioxane, pyrimidine or pyridazine ring and/or ring B standsfor 1,4-phenylene will be readily apparent from the foregoing havingregard to the known methods for the manufacture of such ring systems.

In general, in the manufacture of compounds of formula I which containan ester group or a dioxane ring the esterification or the formation ofthe dioxane ring is advantageously carried out only as a last step.Examples for the manufacture of dioxanes provided by the invention areillustrated in Scheme 9. The pyrimidines and pyridazines provided by theinvention can be obtained by firstly synthesizing the ring systemaccording to known methods and subsequently introducing the alkenylgroup or by using in the formation of the heterocyclic ring a compoundwhich already contains the alkenyl group. The latter method isillustrated in more detail in Scheme 10 for certain pyrimidines.

Compounds of formula I in which R² signifies --OOCR can also bemanufactured from compounds of formula I in which R² signifies --COR byBaeyer-Villiger oxidation with a peracid (e.g. perbenzoic acid) andsubsequent conversion of the epoxide which is thereby simultaneouslyformed into the double bond according to the method described inTetrahedron 36, 557 (1980).

Schemes 1, 2, 6 and 7 apply equally when the cyano group is replaced byalkyl, alkoxy or fluorine. However, it can be advantageous tomanufacture compounds of formula I with different significances for R²according to a common Reaction Scheme and later to introduce the desiredgroup R² in a manner known per se. Examples of these variants areillustrated in Scheme 11.

The starting materials required for the manufacture of fluoro compoundsprovided by the invention (R² =fluorine) are known compounds oranalogues of known compounds or can be obtained in a manner known per sefrom corresponding amines by diazotization with sodium nitrite andhydrochloric acid, conversion into the diazonium tetrafluoroborate withsodium tetrafluoroborate and subsequent heating. The amines can beobtained, for example, starting from the corresponding carboxylic acidsby Hoffmann, Curtius or Schmidt degradation.

The manufacture of the compounds of formula I in which A stands for agroup with 2 to 4 six-membered rings [or the preparation of thecorresponding starting materials required in process variants (a)-(f)]can be carried out in an analogous manner to the manufacture of thebicyclic compounds described above in more detail.

The present invention is also concerned withtrans-4-(trans-5-alkyl-m-dioxan-2-yl)cyclohexanecarbonitriles of theformula ##STR18## wherein R⁸ signifies straight-chain C₁ -C₁₂ -alkyl, aswell as the manufacture of the compounds of formula LXXVIII above,liquid crystalline mixtures which contain these compounds and their usefor electro-optical purposes.

The compounds of formula LXXVIII have at the same time a large positiveanisotropy of the dielectric constants, a small optical anisotropy, lowviscosity (especially when used in mixtures), low threshold potentialsand short response times as well as an improved mesophase behaviour.Further, they have a high chemical stability and only slightconductivity, they are colourless and have a good miscibility with allcustomary liquid crystals and give a high contrast in indicatingdevices. The compounds provided by the invention are therefore very wellsuited for liquid crystalline dielectrics in electro-optical indicatingdevices such as, for example, in rotation cells and guest/host cells,especially in rotation cells.

Preferred compounds of formula LXXVIII are those in which R⁸ signifiesstraight-chain C₃ -C₈ -alkyl.

The compounds of formula LXXVIII can be manufactured by reacting acompound of the formula ##STR19## wherein R⁸ has the above significance,with trans-4-cyanocyclohexanecarboxaldehyde or a suitable acetalthereof. The reaction can be carried out in an analogous manner toprocess variant (f) above.

The compounds of formula I and the compounds of formula LXXVIII can beused in the form of mixtures with other liquid crystalline or non-liquidcrystalline substances such as, for example, with substances from theclasses of Schiff's bases, azobenzenes, azoxybenzenes, phenyl benzoates,cyclohexanecarboxylic acid phenyl esters, cyclohexanecarboxylic acidcyclohexyl esters, biphenyls, terphenyls, phenylcyclohexanes, cinnamicacid derivatives, phenylpyrimidines, diphenylpyrimidines,cyclohexylphenylpyrimidines, phenyldioxanes,2-cyclohexyl-1-phenylethanes, 1,2-dicyclohexylethanes and the like. Suchsubstances are known to the person skilled in the art and many of themare, moreover, commercially available. When non-liquid crystallinecomponents are used care should, however, be taken that additionalliquid crystalline compounds are used in sufficient amount such that thetotal mixture has a sufficiently large mesophase range. Of course, themixtures provided by the invention can also contain at the same time oneor more compounds of formula I and one or more compounds of formulaLXXVIII.

Having regard to the favourable properties of the compounds of formula Iand to their good miscibility, the mixtures provided by the inventioncan also consist solely of two or more compounds of formula I. Themixtures provided by the invention therefore conveniently contain about1-100 wt.%, preferably about 5-70 wt.% and particularly about 10-50 wt.%of compounds of formula I. Besides one or more compounds of formula Ithe mixtures provided by the invention contain, optionally, preferablyone or more compounds of the formula ##STR20## wherein ring B¹ denotes1,4-phenylene or trans-1,4-cyclohexylene, R⁹ denotes straight-chain C₂-C₇ -alkyl, R¹⁰ denotes cyano or straight-chain C₁ -C₆ -alkoxy, R¹¹denotes cyano or straight-chain C₁ -C₇ -alkyl or C₁ -C₇ -alkoxy and R¹²and R¹³ denote straight-chain C₁ -C₇ -alkyl; p stands for 0 or 1; R¹⁴signifies trans-4-alkylcyclohexyl, 4'-alkyl-4-biphenylyl,p-(trans-4-alkylcyclohexyl)phenyl, 2-(trans-4-alkylcyclohexyl)ethyl orp-[2-(trans-4-alkylcyclohexyl)ethyl]phenyl and R¹⁵ signifiestrans-4-alkylcyclohexyl, or R¹⁴ signifies trans-4-alkylcyclohexyl andR¹⁵ signifies p-(trans-4-alkylcyclohexyl)phenyl,p-[2-(trans-4-alkylcyclohexyl)ethyl]phenyl or4'-(trans-4-alkylcyclohexyl)-4-biphenylyl, or R¹⁴ signifiesp-alkylphenyl and R¹⁵ signifiesp-[2-(trans-4-alkylcyclohexyl)ethyl]phenyl, and the alkyl groups in R¹⁴and R¹⁵ are straight-chain C₁ -C₇ -alkyl; one of the symbols Z¹ and Z²represents --COO-- or --OOC-- and the remainder of the symbols Z¹, Z²,Z³ and Z⁴ represent single covalent bonds or one of these symbols alsorepresents --CH₂ CH₂ --; the rings B¹ and B⁵ in formula XCI denotes agroup of the formula ##STR21## or trans-1,4-cyclohexylene; the rings B²,B³ and B⁴ represent a group of formula XCII or, insofar as they are notlinked with at least one of the other two of these rings by a singlecovalent bond, also trans-1,4-cyclohexylene; Y signifies hydrogen or onone of the rings of formula XCII, which is not linked with a furtherring via a single covalent bond, also fluorine, chlorine or methyl; R¹⁶and R¹⁷ denote straight-chain C₁ -C₇ -alkyl or on a ring of formula XCIIalso straight-chain C₁ -C₇ -alkoxy.

The compounds of formulae LXXX-XC are known or can be prepared fromknown compounds by conventional techniques.

The esters of formula XCI are novel, but they can be obtained accordingto esterification methods which are known per se. The starting materialsrequired for the preparation of the esters of formula XCI are known orare analogues of known compounds and can be prepared according to knownmethods.

The mixtures with compounds of formula LXXVIII contain, besides one ormore compounds of formula LXXVIII, preferably one or more compounds offormulae LXXX-XCI. The amount of compounds of formula LXXVIIIconveniently amounts to about 1-50 wt.%, preferably about 5-30 wt.%.

Further, the mixtures provided by the invention can contan suitableoptically active compounds (e.g. optically active biphenyls) and/ordichroic colouring substances (e.g. azo, azoxy or anthraquinonecolouring substances). The amount of such compounds is determined by thesolubility and the desired pitch, colour, extinction and the like. Theamount of optically active compounds preferably amounts to a maximum ofabout 4 wt.% and the amount of dichroic colouring substances preferablyamounts to a maximum of about 10 wt.%.

The manufacture of the liquid crystalline mixtures provided by theinvention can be carried out in a manner known per se; for example, byheating a mixture of the ingredients to a temperature barely above theclearing point and subsequently cooling the mixture.

The manufacture of electro-optical devices which contain a mixtureprovided by the invention as the dielectric can also be carried out in amanner known per se; for example, by evacuating a suitable cell andintroducing the mixture into the evacuated cell.

The invention is also concerned with all novel compounds, mixtures,processes, uses and devices as described herein.

Mixtures 1-4 hereinafter are examples of preferred mixtures provided bythe invention. V₁₀ denotes the threshhold potential for 10%transmission, η denotes the viscosity (bulk viscosity) and t_(on)denotes the switching-on time and t_(off) denotes the switching-off time(in a rotation cell with 2.5. V₁₀ and tilt angle 0°). The measurementswere carried out at 22° C.

    ______________________________________    Mixture 1    ______________________________________    19.0 wt. % of                 4-ethoxy-1-[2-(trans-4-pentylcyclohexyl)-                 ethyl]benzene,    3.5 wt. % of 4-cyano-4"-pentyl-p-terphenyl,    3.5 wt. % of 4-cyano-4'-(trans-4-pentylcyclohexyl)-bi-                 phenyl,    3.0 wt. % of p-[trans-4-(2-(trans-4-pentylcyclohexyl)-                 ethyl)cyclohexyl]benzonitrile,    8.0 wt. % of 1-[2-(trans-4-butylcyclohexyl)ethyl]-4-                 (trans-4-pentylcyclohexyl)benzene,    23.0 wt. % of                 p-[trans-4-(trans-1-butenyl)cyclohexyl]-                 benzonitrile,    40.0 wt. % of                 p-[trans-4-(trans-1-pentenyl)cyclohexyl]-                 benzonitrile;    mp. < -20° C., cl.p. 78° C., nematic; V.sub.10 = 2.18 V,    t.sub.on =    23 ms, t.sub.off = 41 ms.    ______________________________________    Mixture 2    ______________________________________    10.0 wt. % of               p-(5-butyl-2-pyrimidinyl)benzonitrile,    4.0 wt. % of               p-(5-heptyl-2-pyrimidinyl)benzonitrile,    9.0 wt. % of               trans-4-butylcyclohexanecarboxylic acid p-               pentyloxyphenyl ester,    13.0 wt. % of               trans-4-pentylcyclohexanecarboxylic acid p-               propoxyphenyl ester,    21.0 wt. % of               4-ethoxy-1-[2-(trans-4-propylcyclohexyl)-               ethyl]benzene,    4.0 wt. % of               4-cyano-4'-(trans-4-pentylcyclohexyl)bi-               phenyl,    6.0 wt. % of               p-[5-(trans-4-ethylcyclohexyl)-2-pyrimi-               dinyl]benzonitrile,    6.5 wt. % of               p-[trans-4-(trans-1-propenyl)cyclohexyl]-               benzonotrile,    26.5 wt. % of               p-[trans-4-(trans-1-butenyl)cyclohexyl]-               benzonitrile;    m.p. < -20° C., cl.p. 60°  C., nematic; η = 26.5 cp,    V.sub.10 = 1.50 V.    ______________________________________    Mixture 3    ______________________________________    17.5 wt. % of              p-(5-butyl-2-pyrimidinyl)benzonitrile,    10.0 wt. % of              p-(5-heptyl-2-pyrimidinyl)benzonitrile,     6.5 wt. % of              p-ethylbenzoic acid p'-cyanophenyl ester,     8.0 wt. % of              4-cyano-4'-(trans-4-pentylcyclohexyl)biphenyl,    10.0 wt. % of              p-[5-(trans-4-ethylcyclohexyl)-2-pyrimidinyl]-              benzonitrile,    14.5 wt. % of              p-[trans-4-(trans-1-propenyl)cyclohexyl]-              benzonitrile,     9.5 wt. % of              p-[trans-5-(trans-1-pentenyl)-m-dioxan-2-yl]-              benzonitrile,    24.0 wt. % of              p-[trans-5-(trans-1-hexenyl)-m-dioxan-2-yl]-              benzonitrile;    m.p. about -10° C., cl.p. 80.4° C., nematic; V.sub.10 =    1.31 V.    ______________________________________    Mixture 4    ______________________________________    16.3 wt. % of               p-(5-butyl-2-pyrimidinyl)benzonitrile,    9.3 wt. % of               p-(5-heptyl-2-pyrimidinyl)benzonitrile,    6.1 wt. % of               p-ethylbenzoic acid p'-cyanophenyl ester,    7.0 wt. % of               4-ethyl-1-[2-(trans-4-propylcyclohexyl)-               ethyl]benzene,    7.4 wt. % of               4-cyano-4'-(trans-4-pentylcyclohexyl)biphenyl,    9.3 wt. % of               p-[5-(trans-4-ethylcyclohexyl)-2-pyrimidinyl]-               benzonitrile,    13.5 wt. % of               p-[trans-4-(trans-1-propenyl)cyclohexyl]-               benzonitrile,    8.8 wt. % of               p-[trans-5-(trans-1-pentenyl)-m-dioxan-2-yl]-               benzonitrile,    22.3 wt. % of               p-[trans-5-(trans-1-hexenyl)-m-dioxan-2-yl]-               benzonitrile;    m.p. < -20° C., cl.p. 72° C., nematic; V.sub. 10 = 1.29    ______________________________________    V.

The following examples illustrate the manufacture of the inventivecompounds. In the examples, C denotes a crystalline phase, S denotes asmectic phase, S_(B) denotes a smectic B phase, N denotes a nematicphase and I denotes the isotropic phase. Unless otherwise stated,percentages and ratios relating to solvent mixtures are expressed involume, purity data determined by gas chromatography are expressed inarea % and remaining percentages and ratios are expressed in weight,temperatures are in degrees Celsius (°C.), normal pressure is about 1atmosphere and room temperature is about 23° C. The petroleum ether is awell-known mixture of low-boiling hydrocarbons. Unless indicatedotherwise, the examples were carried out as written. The term"working-up" means, in the case of working-up of a reaction mixture,extraction of the product from the reaction mixture or, in the case ofworking-up of a mother liquor, crystallization of further product fromthe concentrated mother liquor.

EXAMPLE 1

A solution of 7.1 mmol of ethylmagnesium bromide (prepared from 172 mgof magnesium and 530 μl of ethyl bromide) in 20 ml of absolutetetrahydrofuran was placed at -78° C. while gassing with argon in asulphonation flask provided with a thermometer, dropping funnel andserum cap and treated in sequence with 3.6 ml of a 0.48M solution ofdilithium tetrachlorocuprate in absolute tetrahydrofuran and with asolution of 500 mg ofp-[trans-4-(3-acetoxy-trans-1-propenyl)cyclohexyl]benzonitrile in 10 mlof absolute tetrahydrofuran. After completion of the addition, themixture was warmed to -15° C., stirred at this temperature for 1.5hours, subsequently treated with 20 ml of saturated ammonium chloridesolution and stirred at room temperature for a further 1 hour. Theaqueous phase, which was now deep blue, was separated and extractedtwice with 50 ml of diethyl ether each time. The organic phases werewashed twice with 50 ml of water each time, dried over magnesiumsulphate and concentrated. Low-pressure chromatography (0.5 bar) of theresidue (0.4 g) on silica gel with ethyl acetate/petroleum ether (vol.3:97) gave 375 mg of crudep-[trans-4-(trans-1-pentenyl)cyclohexyl]benzonitrile which, according toanalysis by gas chromatography, was contaminated to 8.5% withp-[trans-4-(trans-1-pentenyl)cyclohexyl]propiophenone and to 4.0% withp-[trans-4-(1-vinylpropyl)cyclohexyl]benzonitrile. Treatment of thiscrude product with an excess of sodium borohydride in methanol at 0° C.(in order to reduce the propiophenone), working-up, low-pressurechromatography (0.5 bar) on silica gel with ethyl acetate/petroleumether (vol. 1:9) and finally recrystallization from methanol at -78° C.gave p-[trans-4-(trans-1-pentenyl)cyclohexyl]benzonitrile in a purity of98.6%; m.p. (C--N) 15.5° C., cl.p. (N--I) 57.0° C.

In the chromatographic separation of the crude product on silica gelwith ethyl acetate/petroleum ether (vol. 1:9) there was obtained as asecond fraction1-(1-hydroxypropyl)-4-[trans-4-(trans-1-pentenyl)cyclohexyl]benzenewhich was dissolved in acetone at 0° C. and oxidized to the ketone bythe addition of chromic acid (until the orange colour remained). Theexcess chromic acid was decomposed with isopropanol. After working-upand recrystallization, there was finally obtained purep-[trans-4-(trans-1-pentenyl)cyclohexyl]propiophenone of melting point(C--N) 60.5° C. and clearing point (N--I) 75.0° C.

The p-[trans-4-(3-acetoxy-trans-1-propenyl)cyclohexyl]benzonitrile usedas the starting material was prepared as follows:

(a) 10.4 g of triphenyl-methoxymethyl-phosphonium chloride weresuspended in 60 ml of t-butyl methyl ether while gassing with argon in asulphonation flask provided with a thermometer, mechanical stirrer,dropping funnel and solid substance addition tube and treated at -10° C.within 10 minutes with 3.6 g of solid potassium t-butylate. Aftercompletion of the addition, the mixture was stirred at -10° C. to 0° C.for a further 30 minutes and then the deep orange, heterogenous mixturewas treated dropwise at 0° C. with a solution of 4.2 g of4-(p-cyanophenyl)cyclohexanone in 50 ml of absolute tetrahydrofuran. Themixture was subsequently stirred at room temperature for a further 2hours, then poured into 500 ml of hexane and filtered. Low-pressurechromatography (0.5 bar) of the concentrated residue (7.1 g) on silicagel with ethyl acetate/petroleum ether (vol. 5:95) gave 4.5 g (94%) ofp-[4-(methoxymethylene)cyclohexyl]benzonitrile as a colourless oil;purity 95%, Rf-value (ethyl acetate/petroleum ether vol. 1:9) 0.30.

(b) A mixture of 4.2 g of p-[4-(methoxymethylene)cyclohexyl]benzonitrileand 100 ml of tetrahydrofuran/2N hydrochloric acid (vol. 4:1) was heatedto reflux for 30 minutes in a round flask. The mixture was subsequentlypoured into 100 ml of water and extracted three times with 100 ml ofdiethyl ether each time. The organic phases were washed once with 100 mlof water, dried over magnesium sulphate and concentrated. There wereobtained 3.9 g (100%) of 4-(p-cyanophenyl)cyclohexanecarboxaldehyde as acolourless oil which was used in the next step without furtherpurification: trans/cis ratio about 3:1, Rf-value (ethylacetate/petroleum vol. 3:7) 0.41. By recrystallization from hexane therecould be obtained pure trans-4-(p-cyanophenyl)cyclohexanecarboxaldehyde;m.p. 57.1° C.

(c) A mixture of 3.9 g of the 4-(p-cyanophenyl)cyclohexanecarboxaldehydeobtained above and 272 mg of powdered potassium carbonate in 60 ml ofethanol was placed at room temperature while gassing with argon in asulphonation flask provided with a solid substance addition tube andtreated within 15 minutes with 7.6 g of solidethoxycarbonylmethylene-triphenylphosphorane. The mixture wassubsequently stirred at room temperature for 2 hours, then freed fromethanol on a rotary evaporator, the residue was taken up in 100 ml ofwater and extracted three times with 100 ml of methylene chloride eachtime. The organic phases were washed twice with 100 ml of water eachtime, dried over magnesium sulphate and concentrated. Low-pressurechromatography (0.5 bar) of the residue (12 g) on silica gel withtoluene/petroleum ether/ethyl acetate (vol. 5:4:1) gave 5.2 g of acrystalline mass which, after crystallization from 500 ml of hexane,yielded 3.9 g (75%) of ethyltrans-3-[trans-4-(p-cyanophenyl)cyclohexyl]acrylate as colourlesscrystals of melting point 125° C.

(d) A solution 1.0 g of ethyltrans-3-[trans-4-(p-cyanophenyl)cyclohexyl]acrylate in 25 ml ofmethylene chloride was placed at -78° C. while gassing with argon in asulphonation flask provided with a thermometer and serum cap and treatedwithin 10 minutes with 15.0 ml of a 0.84M solution ofdiisobutylaluminium hydride in toluene. After completion of theaddition, the mixture was warmed to -10° C., stirred at this temperaturefor further 30 minutes, poured into 100 ml of 0.2N sulphuric acid andextracted twice with 50 ml of methylene chloride each time. The organicphases were washed with 50 ml of water, dried over magnesium sulphateand concentrated. The residue (about 850 mg) was dissolved in 30 ml ofmethylene chloride and treated in sequence with 0.5 ml of aceticanhydride and 45 mg of 4-(dimethylamino)pyridine. The mixture wasstirred at room temperature for 1 hour, then poured into 50 ml ofsaturated, aqueous copper sulphate solution and extracted twice with 50ml of methylene chloride each time. The organic phases were washed twicewith 50 ml of water each time, dried over magnesium sulphate andconcentrated. Low-pressure chromatography (0.5 bar) of the residue (0.95g) on silica gel with ethyl acetate/petroleum ether (vol. 1:9) gave 720mg (71%) ofp-[trans-4-(3-acetoxy-trans-1-propenyl)cyclohexyl]benzaldehyde; purity99.9%, Rf-value (ethyl acetate/petroleum ether vol. 1:9) 0.31.

(e) A solution of 513 mg of hydroxylammonium chloride in 5 ml of waterwas placed while gassing with argon in a sulphonation flask providedwith a mechanical stirrer and treated at room temperature with asolution of 2.0 g ofp-[trans-4-(3-acetoxy-trans-1-propenyl)cyclohexyl]benzaldehyde in 10 mlof pyridine. The mixture was stirred for 1 hour and then treated insequence with 350 mg of copper sulphate pentahydrate and a solution of2.1 ml of triethylamine in 10 ml of methylene chloride. After theinitially inky blue colour of the copper-pyridine complex had turnedolive-green, a solution of 1.74 g of dicyclohexylcarbodiimide in 20 mlof methylene chloride was added. The mixture was subsequently stirred atroom temperature for a further 3 hours and then filtered. The filtratewas poured into 100 ml of water and extracted three times with 100 ml ofmethylene chloride each time. The organic phases were washed twice with50 ml of water each time, dried over magnesium sulphate andconcentrated. Low-pressure chromatography (0.5 bar) of the residue (2.75g) on silica gel with toluene/ethyl acetate (vol. 9:1) gave 2.26 g(114%) of p-[trans-4-(3-acetoxy-trans-1-propenyl)cyclohexyl]benzonitrileas colourless crystals which still contained somedicyclohexylcarbodiimide as the sole impurity. This material wasprocessed without additional purification. Rf-value (toluene/ethylacetate vol. 9:1) 0.33.

The following compound was manufactured in an analogous manner:

p-[Trans-4-(trans-1-butenyl)cyclohexyl]benzonitrile, m.p. (C--N) 44.2°C., cl.p. (N--I) 49.5° C.

EXAMPLE 2

A mixture of 235 mg ofp-[trans-4-(trans-1-pentenyl)cyclohexyl]propiophenone (preparedaccording to Example 1), 0.161 ml of hydrazine hydrate, 5 ml ofdiethylene glycol and 5 ml of ethanol was heated to reflux for 30minutes under an argon atmosphere in a round flask provided with areflux condenser. The mixture was then treated with 195 mg of solidpotassium hydroxide and subsequently gradually heated to 200° C., whiledistilling off the ethanol, and held at this temperature for 2 hours.The cooled mixture was poured into 50 ml of water and extracted threetimes with 50 ml of petroleum ether each time. The organic phases werewashed three times with 50 ml of water each time, dried over magnesiumsulphate and concentrated. Low-pressure chromatography (0.5 bar) of theresidue with hexane on a short column of silica gel gave 185 mg (83%) of4-propyl-1-[trans-4-(trans-1-pentenyl)cyclohexyl]benzene as a colourlessliquid; purity 98.6%, m.p. (C--I) 7.0° C.

EXAMPLE 3

A mixture of 3.8 g of 4-(p-cyanophenyl)cyclohexanecarboxaldehyde(prepared according to Example 1), 10.3 g of propyltriphenylphosphoniumbromide and 12.3 g of potassium carbonate in 200 ml of dioxan was heatedto reflux for 25 hours while gassing with argon in a round flaskprovided with a reflux condenser. The cooled mixture was subsequentlyfiltered and concentrated. The residue was taken up in 150 ml of waterand extracted three times with 150 ml of diethyl ether each time. Theorganic phases were washed twice with 100 ml of water each time, driedover magnesium sulphate and concentrated. Low-pressure chromatography(0.5 bar) of the residue (10.5 g) with ethyl acetate/petroleum ether(vol. 3:97) gave 2.35 g (55%) of a colourless, semi-crystalline masswhich, according to analysis by gas chromatography, consisted of 80.3wt.% of p-[trans-4-(cis-1-butenyl)cyclohexyl]benzonitrile, 17.5 wt.% ofp-[trans-4-(trans-1-butenyl)cyclohexyl]benzonitrile and 2.2 wt.% ofp-[cis-4-(cis-1-butenyl)cyclohexyl]benzonitrile. By additionallow-pressure chromatography (0.5 bar) of this material on silica gelcoated with 10% silver nitrate using ethyl acetate/petroleum ether (vol.3:97) and by subsequent crystallization from methanol at -78° C. therecould be isolated purep-[trans-4-(trans-1-butenyl)cyclohexyl]benzonitrile; m.p. (C--N) 44.2°C., cl.p. (N--I) 49.5° C.

EXAMPLE 4

(a) 4.0 g of 4-(p-cyanophenyl)cyclohexanecarboxaldehyde (preparedaccording to Example 1) were dissolved in 50 ml of 0.1N methanolicpotassium hydroxide solution while gassing with argon in a sulphonationflask provided with a thermometer and the solution was treatedportionwise at 0° C. within 20 minutes with 711 mg of sodiumborohydride. The mixture was stirred at 0° C. for a further 10 minutes,neutralized with 1N hydrochloric acid and concentrated on a rotaryevaporator. The residue was taken up in 200 ml of water and extractedthree times with 100 ml of methylene chloride each time. The organicphases were washed twice with 100 ml of water each time, dried overmagnesium sulphate and concentrated. A single crystallization of theresidue (4.2 g) from 90 ml of ethyl acetate/petroleum ether (vol. 1:2)at 0° C. gave 3.27 g (77%) ofp-[trans-4-(hydroxymethyl)cyclohexyl]benzonitrile as colourless crystalsof melting point 109.8° C.; purity 99.4%.

(b) A solution of 3.0 g ofp-[trans-4-(hydroxymethyl)cyclohexyl]benzonitrile in 5 ml of pyridinewas placed at 0° C. while gassing with argon in a sulphonation flaskprovided with a mechanical stirrer, thermometer and dropping funnel andtreated within 5 minutes with a solution of 4.4 g of p-tosyl chloride in10 ml of pyridine. After completion of the addition, the cooling bathwas removed and the mixture was stirred at room temperature for 15hours. The mixture was freed from pyridine on a rotary evaporator andthe residue was taken up in 100 ml of water and extracted three timeswith 100 ml of methylene chloride each time. The organic phases werewashed twice with 100 ml of water each time, dried over magnesiumsulphate and concentrated. Low-pressure chromatography (0.5 bar) of theresidue (5.0 g) on silica gel with ethyl acetate/petroleum ether (vol.1:4) gave 4.35 g (95%) ofp-[trans-4-(p-tosyloxymethyl)cyclohexyl]benzonitrile as colourlesscrystals; Rf-value (ethyl acetate/petroleum ether vol. 3:7) 0.38.

(c) A mixture of 3.8 g ofp-[trans-4-(p-tosyloxymethyl)cyclohexyl]benzonitrile, 2.3 g of sodiumiodide and 100 ml of acetone was heated to reflux for 15 hours whilegassing with argon in a round flask provided with a reflux condenser.After filtration and concentration of the mixture on a rotaryevaporator, the residue was taken up in 100 ml of water and extractedthree times with 100 ml of diethyl ether each time. The organic phaseswere washed twice with 100 ml of water each time, dried over magnesiumsulphate and concentrated. Low-pressure chromatography (0.5 bar) of theresidue on silica gel with toluene gave 3.19 g (95%) ofp-[trans-4-(iodomethyl)cyclohexyl]benzonitrile as colourless crystals;Rf-value (ethyl acetate/petroleum ether vol. 1:9) 0.30.

EXAMPLE 5

A suspension of 2.51 g of methyltriphenylphosphonium bromide in 80 ml ofabsolute tetrahydrofuran was placed at -20° C. while gassing with argonin a sulphonation flask provided with a dropping funnel and thermometerand treated with 7.6 ml of an about 0.8M solution of butyl lithium inhexane. After stirring at -20° C. for 30 minutes, a solution of 1.0 g oftrans-4-(p-cyanophenyl)cyclohexanecarboxaldehyde in 10 ml of absolutetetrahydrofuran was added dropwise at -20° C. within 5 minutes to theyellow mixture, whereby the yellow colour disappeared. The mixture wasnow stirred at -20° C. for a further 30 minutes and then poured into 100ml of water and extracted three times with 100 ml of diethyl ether eachtime. The organic phases were washed twice with 100 ml of water eachtime, dried over magnesium sulphate and concentrated. Low-pressurechromatography (0.5 bar) of the residue (2.3 g) on silica gel with ethylacetate/petroleum ether (vol. 3:97) gave 897 mg (91%) ofp-(trans-4-vinylcyclohexyl)benzonitrile as colourless crystals; purity99.4%. By additional crystallization from 22 ml of methanol there wasobtained p-(trans-4-vinylcyclohexyl)benzonitrile in a purity of 99.95%;m.p. (C--I) 56.4° C., cl.p. 28.5° C.

EXAMPLE 6

A suspension of 3.6 g of butyltriphenylphosphonium bromide in 40 ml oft-butyl methyl ether was placed at room temperature while gassing withargon in a sulphonation flask provided with a thermometer, mechanicalstirrer, dropping funnel and solid substance addition tube, treated with1.01 g of potassium t-butylate and stirred at room temperature for afurther 1 hour. The deep orange, heterogeneous mixture was subsequentlycooled to -60° C. and treated within 15 minutes with a solution of 1.28g of trans-4-(p-cyanophenyl)cyclohexanecarboxaldehyde in 10 ml oft-butyl methyl ether. The mixture was stirred for a further 60 minuteswhile warming slowly to -30° C., then poured into 100 ml of water andextracted three times with 50 ml of diethyl ether each time. The organicphases were washed once with 50 ml of water, dried over magnesiumsulphate and concentrated. Low-pressure chromatography (0.5 bar) of theresidue (3.45 g) on silica gel with ethyl acetate/petroleum ether (vol.3:97) gave 1.52 g (99%) ofp-[trans-4-(1-pentenyl)cyclohexyl]benzonitrile(trans-1-pentenyl/cis-1-pentenyl ratio about 5:95) as a colourless oil;Rf-value (ethyl acetate/petroleum ether vol. 3:97) 0.19.

The following compounds were manufactured in an analogous manner:

p-[Trans-4-(1-propenyl)cyclohexyl]benzonitrile,

p-[trans-4-(1-butenyl)cyclohexyl]benzonitrile,

p-[trans-4-(1-hexenyl)cyclohexyl]benzonitrile,

p-[trans-4-(1-heptenyl)cyclohexyl]benzonitrile.

EXAMPLE 7

A mixture of 3.79 g of p-[trans-4-(1-hexenyl)cyclohexyl]benzonitrile(prepared according to Example 6; trans-1-hexenyl/cis-1-hexenyl ratioabout 5:95) and 758 mg of benzenesulphonic acid in 50 ml of 1,4-dioxanwas boiled under reflux for 15 hours while gassing with argon in a roundflask provided with a magnetic stirrer and reflux condenser. A further379 mg of benzenesulphonic acid were subsequently added and the mixturewas heated to reflux for a further 4 hours. The cooled mixture was thenpoured into 50 ml of 1N sodium hydroxide solution and extracted threetimes with 100 ml of hexane each time. The organic phases were washedtwice with 50 ml of water each time, dried over magnesium sulphate andconcentrated. Three-fold crystallization of the quantitatively obtained,equilibrated, olefine mixture (trans-1-hexenyl/cis-1-hexenyl ratio80.4:19.6) from methanol finally gave 1.74 g (46%) ofp-[trans-4-(trans-1-hexenyl)cyclohexyl]benzonitrile (containing 0.3% ofcis-1-hexenyl isomer) of melting point (C--N) 14.3° C. and cl.p. (N--I)39.5° C. The mother liquors were not worked-up. However, if desired,these can be again equilibrated and the equilibrated mixture can besubjected to crystallization.

The following compounds were manufactured in an analogous manner:

p-[Trans-4-(trans-1-propenyl)cyclohexyl]benzonitrile; m.p. (C--N) 66.3°C., cl.p. (N--I) 73.0° C.,

p-[trans-4-(trans-1-butenyl)cyclohexyl]benzonitrile; m.p. (C--N) 45.1°C., cl.p. (N--I) 51.8° C.,

p-[trans-4-(trans-1-pentenyl)cyclohexyl]benzonitrile; m.p. (C--N) 15.6°C., cl.p. (N--I) 58.5° C.,

p-[trans-4-(trans-1-heptenyl)cyclohexyl]benzonitrile; m.p. (C--N) 17.9°C., cl.p. (N--I) 49.2° C.

EXAMPLE 8

A mixture of 2.75 g ofp-[trans-4-(erythro-1,2-dibromopentyl)cyclohexyl]benzonitrile and 20 mlof glacial acetic acid was treated at room temperature with 2.42 g ofzinc powder while gassing with argon in a sulphonation flask providedwith a mechanical stirrer and thermometer and then stirred for 2 hours,whereby the mixture warmed to 33° C. and the educt gradually passed intosolution. The mixture was subsequently poured into 100 ml of water andextracted three times with 100 ml of petroleum ether each time. Theorganic phases were washed twice with 100 ml of water each time and oncewith 50 ml of saturated sodium hydrogen carbonate solution, dried overmagnesium sulphate and concentrated. There were thus obtained 1.43 g(99%) of p-[trans-4-(trans-1-pentenyl)cyclohexyl]benzonitrile in apurity of 99.5%; m.p. (C--N) 15.6° C., cl.p. (N--I) 58.5° C.

The p-[trans-4-(erythro-1,2-dibromopentyl)cyclohexyl]benzonitrile usedas the starting material was prepared as follows:

(a) A mixture of 1.51 g of 90% m-chloroperbenzoic acid and 3.0 g ofpowdered potassium carbonate in 60 ml of methylene chloride was placedat 0° C. while gassing with argon in a sulphonation flask provided witha thermometer, dropping funnel and mechanical stirrer and treated within15 minutes with a solution of 2.0 g ofp-[trans-4-(1-pentenyl)cyclohexyl]benzonitrile (prepared according toExample 6; trans-1-pentenyl/cis-1-pentenyl ratio about 5:95) in 20 ml ofmethylene chloride. The cooling bath was subsequently removed and themixture was treated after a total of 75 minutes and 105 minutes with ineach case a further 0.75 g of 90% m-chloroperbenzoic acid. The mixturewas stirred at room temperature for a further 60 minutes, then pouredinto 50 ml of 10% (wt./vol.) sodium thiosulphate solution and extractedthree times with 100 ml of methylene chloride each time. The organicphases were washed with 50 ml of saturated sodium hydrogen carbonatesolution, dried over magnesium sulphate and concentrated. There was thusobtained 2.1 g (98%) ofp-[trans-4-(1,2-epoxypentyl)cyclohexyl]benzonitrile,(trans-1,2-epoxypentyl/cis-1,2-epoxypentyl ratio about 5:95) as acolourless oil; Rf-values (ethyl acetate/petroleum ether vol.10:90):trans-1,2-epoxypentyl isomer 0.17, cis-1,2-epoxypentyl isomer 0.14.

(b) A solution of 2.46 g of triphenylphosphine in 30 ml of methylenechloride was placed at 0° C. while gassing with argon in a round flaskprovided with a dropping funnel and treated dropwise with an about 1Msolution of bromine in methylene chloride until a faint yellow colourremained. The solution was subsequently concentrated cautiously on arotary evaporator and then dried in a high vacuum. The crystallineresidue obtained was suspended in 30 ml of benzene, treated with asolution of 2.1 g of p-[trans-4-(1,2-epoxypentyl)cyclohexyl]benzonitrilein 10 ml of benzene and heated to reflux for 3 hours. Filtration of thewarm solution on silica gel with toluene gave 3.0 g of crystalline crudeproduct which, after low-pressure chromatography (0.5 bar) on silica gelwith hexane/toluene (vol. 1:1), yielded 2.61 g (81%) of almost purep-[trans-4-(erythro-1,2-dibromopentyl)cyclohexyl]benzonitrile ascolourless crystals. By recrystalization from 90 ml of petroleumether/ethyl acetate (vol. 2:1) there were finally obtained 2.09 g (65%)of very pure erythro dibromide; m.p. 140.9° C.

The following compounds were manufacture in an analogous manner:

p-[Trans-4-(trans-1-propenyl)cyclohexyl]benzonitrile; m.p. (C--N) 66.3°C., cl.p. (N--I) 73.0° C.,

p-[trans-4-(trans-1-butenyl)cyclohexyl]benzonitrile; m.p. (C--N) 45.1°C., cl.p. (N--I) 51.8° C.,

p-[trans-4-(trans-1-hexenyl)cyclohexyl]benzonitrile; m.p. (C--N) 14.4°C., cl.p. (N--I) 39.2° C.

p-[trans-4-(trans-1-heptenyl)cyclohexyl]benzonitrile; m.p. (C--N) 17.9°C., cl.p. (N--I) 49.2° C.

EXAMPLE 9

In an analogous manner to Examples 1, 5, 6 and 8,4-[2-(p-cyanophenyl)ethyl]cyclohexanone was converted intotrans-4-[2-(p-cyanophenyl)ethyl]cyclohexanecarboxaldehyde and the latterwas converted intop-[2-(trans-4-(trans-1-alkenyl)cyclohexyl)ethyl]benzonitriles.

The 4-[2-(p-cyanophenyl)ethyl]cyclohexanone used as the startingmaterial was prepared as follows:

(a) 149 g of methoxymethyl-triphenylphosphonium chloride and 860 ml oft-butyl methyl ether were placed in a sulphonation flask at roomtemperature while stirring and gassing with nitrogen, the suspension wascooled to -10° C. and treated within 10 minutes with 51.6 g of potassiumt-butylate. The suspension was stirred at -10° C. to 0° C. for a further30 minutes and then treated dropwise within 45 minutes at 0° C. with asolution of 47.3 g of 4,4-ethylenedioxycyclohexanone in 720 ml oftetrahydrofuran. The orange suspension was stirred at room temperaturefor a further 2 hours, then poured into 5 l of hexane, stirred for 10minutes and suction filtered. The filtrate was concentrated in vacuo andthe resulting yellow-brownish oil (104.1 g) was treated with 500 ml ofhexane and suction filtered. The filtrate was concentrated in vacuo,61.7 g of a yellow-brownish oil being obtained. Chromatographicseparation of this crude product on silica gel with methylenechloride/acetone (vol. 98:2 and 95:5) finally gave 53.5 g of1,1-ethylenedioxy-4-(methoxymethylene)cyclohexane as a colourless oil.

(b) A mixture of 28.2 g of1,1-ethylenedioxy-4-(methoxymethylene)cyclohexane, 770 ml of glacialacetic acid and 385 ml of water was heated to reflux for 1 hour whilegassing with nitrogen in a round flask. Thereafter the yellowish clearsolution was cooled to room temperature, diluted with 800 ml of waterand extracted three times with 700 ml of methylene chloride each time.The organic phases were washed twice with 500 ml of 10% (wt./vol,)sodium carbonate solution each time, dried over sodium sulphate,filtered and concentrated. Chromatographic separation of the resultingbrownish liquid (18.5 g) on silica gel with methylene chloride as theeluent finally gave 16.7 g of 4-formylcyclohexanone as a brownishliquid.

(c) 63.3 g of p-cyanobenzyl-triphenylphosphonium chloride, 17.2 g ofpotassium t-butylate and 195 ml of ethylene glycol dimethyl ether wereplaced while stirring and gassing with nitrogen in a sulphonation flask,whereby the internal temperature rose to 44° C. The brown suspension wascooled to 0° C. and treated within 2 minutes with a solution of 16.7 gof 4-formylcyclohexanone in 100 ml of ethylene glycol dimethyl ether.The cooling bath was then removed and the mixture was stirred at roomtemperature for a further 3.5 hours. The suspension was subsequentlypoured into 500 ml of water and extracted three times with 600 ml ofmethylene chloride each time. The organic phases were washed twice with500 ml of 10% (wt./vol.) sodium chloride solution each time, dried oversodium sulphate, filtered and concentrated, there being obtained 76.9 gof a brownish paste. Chromatographic separation of this crude product onsilica gel with methylene chloride as the eluent gave 33.0 g of4-[2-(p-cyanophenyl)vinyl]cyclohexanone as a yellow-brownish oil.

(d) A mixture of 33.0 g of 4-[2-(p-cyanophenyl)vinyl]cyclohexanone, 520ml of toluene, 260 ml of ethanol and 3.2 g of palladium/carbon-(5%) wasplaced at room temperature in a round flask provided with a magneticstirrer and the mixture was hydrogenated until the hydrogen uptake cameto a standstill. The black suspension was subsequently suction filtered(rinsing with toluene) and the filtrate was concentrated in vacuo. Theresulting, slightly turbid, yellowish oil (34.1 g) was separated bychromatography on silica gel. Elution with methylene chloride/hexane(vol. 1:1), methylene chloride/hexane (vol. 8:2) and methylene chlorideyielded 25.6 g of a yellowish oil which was crystallized from t-butylmethyl ether. There were thus obtained 22.6 g of4-[2-(p-cyanophenyl)ethyl]cyclohexanone as colourless crystals ofmelting point 62.5°-64.3° C.

The following compounds were manufactured in an analogous manner:

p-[2-(Trans-4-(trans-1-propenyl)cyclohexyl)ethyl]benzonitrile; m.p.(C--I) 61.3° C., cl.p. (N--I) 54.2° C.,

p-[2-(trans-4-(trans-1-butenyl)cyclohexyl)ethyl]benzonitrile; m.p.(C--I) 42.6° C., cl.p. (N--I) 39.7° C.,

p-[2-(trans-1-pentenyl)cyclohexyl)ethyl]benzonitrile; m.p. (C--N) 25.1°C., cl.p. (N--I) 47.5° C.,

p-[2-(trans-4-(trans-1-hexenyl)cyclohexyl)ethyl]benzonitrile; m.p.(C--N) 16.8° C. and 19.7° C. (two modifications), cl.p. (N--I) 34.6° C.,

p-[2-(trans-4-(trans-1-heptenyl)cyclohexyl)ethyl]benzonitrile; m.p.(C--N) 31.6° C., cl.p. (N--I) 43.6° C.

EXAMPLE 10

A mixture of 200 mg of trans-4-(trans-1-pentenyl)cyclohexanol, 245.9 mgof trans-4-pentylcyclohexanecarboxylic acid, 293 mg ofdicyclohexylcarbodiimide, 14.16 mg of 4-(dimethylamino)pyridine and 3 mlof methylene chloride was stirred at room temperature for 25 hours. Themixture was subsequently diluted with diethyl ether, the precipitatedurea was filtered off and the filtrate was concentrated. The residue wastaken up in 40 ml of methylene chloride and washed with 5% hydrochloricacid, sodium hydrogen carbonate solution and sodium chloride solution.The aqueous phases were back-extracted with methylene chloride. Theorganic phases were dried over magnesium sulphate, filtered andconcentrated. Low-pressure chromatography of the resulting, whiteresidue (450 mg) on silica gel with diethyl ether/petroleum ether (vol.3:97) gave 348 mg of white, transparent needles which wererecrystallized from 20 ml of methanol. There were thus obtained 289 mgof trans-4-pentylcyclohexanecarboxylic acidtrans-4-(trans-1-pentenyl)cyclohexyl ester; m.p. (C--S) 39.8° C., cl.p.(S--I) 66.5° C.

The trans-4-(trans-1-pentenyl)cyclohexanol used as the starting materialwas prepared as follows:

(a) 261.2 g of methoxymethyl-triphenylphosphonium chloride weresuspended in 550 ml of t-butyl methyl ether and treated at -10° C. with90.53 g of potassium t-butylate. The cooling bath was removed and themixture was stirred at room temperature for 1 hour. The suspension wassubsequently treated slowly at -10° C. with a solution of 70 g of4,4-ethylenedioxycyclohexanone in 350 ml of tetrahydrofuran, stirred atroom temperature for 1 hour, then treated with water and extracted threetimes with diethyl ether. The organic phases were washed twice withwater and the aqueous phases were back-extracted with diethyl ether. Thecombined organic phases were dried over magnesium sulphate andconcentrated. The crystalline residue obtained was dissolved in ethylacetate, diluted with petroleum ether, filtered and freed from solvent.Distillation of the resulting, yellow oil (100 g) gave in the main run(71° C./0.20-0.17 Torr) 75.28 g (91.17%) of1,1-ethylenedioxy-4-(methoxymethylene)cyclohexane as a clear, colourlessliquid.

(b) A mixture of 10.55 g of1,1-ethylenedioxy-4-(methoxymethylene)cyclohexane, 130 ml of water and200 ml of glacial acetic acid was heated to reflux for 1 hour. Thesolvent was subsequently distilled off on a rotary evaporator and thedistillate was extracted twice with methylene chloride. The distillationresidue (a yellow oil) was diluted with 200 ml of water, neutralizedwith sodium carbonate solution and extracted three times with methylenechloride. The organic phases were washed with saturated sodium carbonatesolution and the aqueous phases were back-extracted with methylenechloride. The organic phases were dried over magnesium sulphate andevaporated. Distillation of the residual, yellow oil gave 6.7 g (93%) of4-formylcyclohexanone at 70° C./0.15 Torr.

(c) A solution of 36.72 g of triphenylphosphine in 200 ml of methylenechloride was treated slowly at -20° C. with 23.22 g of carbontetrabromide and stirred for a further 10 minutes. Subsequently, themixture was added dropwise by means of a cannula to a solution, cooledto -60° C., of 6.30 g of 4-formylcyclohexanone in 100 ml of methylenechloride. The mixture was stirred at -60° C. for a further 15 minutesand then partitioned in water/methylene chloride. The aqueous phaseswere extracted a further twice with methylene chloride. The organicphases were washed twice with water, dried over magnesium sulphate andevaporated. Low-pressure chromatography of the resulting, pale yellowoil (16 g) on silica gel with ethyl acetate/petroleum ether (vol. 10:90)gave 12.08 g (85.8%) of 4-(2,2-dibromovinyl)cyclohexanone as a paleyellow liquid.

(d) A mixture of 2 g of 4-(2,2-dibromovinyl)cyclohexanone, 3.43 g ofethylene glycol, 0.202 g of p-toluenesulphonic acid and 240 ml ofbenzene was boiled at reflux for 5 hours with separation of water. Themixture was subsequently treated with potassium carbonate, stirred for ashort time and left to stand overnight. The mixture was then filteredand the filtrate was freed from solvent on a rotary evaporator. Theresidue was taken up in 200 ml of methylene chloride and washed twicewith dilute sodium hydroxide solution and once with water. The aqueousphases were back-extracted with methylene chloride. The organic phaseswere dried over magnesium sulphate, filtered and evaporated. There werethus obtained 14 g of 1,1-ethylenedioxy-4-(2,2-dibromovinyl)cyclohexaneas a light yellow, crystallizing liquid.

(e) A solution of 14 g of1,1-ethylenedioxy-4-(2,2-dibromovinyl)cyclohexane in 70 ml oftetrahydrofuran was cooled to -20° C. and treated slowly at thistemperature with 76.62 ml of a 1.4M solution of butyl lithium in hexane(exothermic reaction). The cooling bath was removed and the mixture wasleft to warm to 20° C. within about 20 minutes. The mixture wassubsequently treated with 150 ml of water and extracted three times withdiethyl ether. The organic phases were washed twice with water and thewash-water was back-extracted with diethyl ether. The organic phaseswere dried over magnesium sulphate, filtered and evaporated.Low-pressure chromatography of the resulting, yellow liquid (8 g) onsilica gel with ethyl acetate/petroleum ether (vol. 7:93) gave 6.5 g(91%) of 4-ethynyl-1,1-ethylenedioxycyclohexane as a clear liquid.

(f) A solution of 6.5 g of 4-ethynyl-1,1-ethylenedioxycyclohexane in 40ml of tetrahydrofuran was treated at -20° C. with 39.1 ml of a 1.4Msolution of butyl lithium in hexane. Subsequently, the mixture wastreated at 0° C. with 60 ml of hexamethylphosphoric acid triamide (brieftemperature rise to 26° C.) and then dropwise with 6.5 ml of propyliodide. The cooling bath was removed and the mixture was left to warm toroom temperature. A white precipitate formed. After 30 minutes, themixture was treated with 150 ml of water and extracted three times withhexane. The organic phases were washed three times with water and thewash-water was back-extracted with hexane. The organic phases were driedover magnesium sulphate, filtered and freed from solvent on a rotaryevaporator. Low-pressure chromatography of the resulting, yellow liquid(9 g) on silica gel with ethyl acetate/petroleum ether (vol. 10:90) andtreatment with active carbon gave 6.23 g (76.5%) of 1,1-ethylenedioxy-4-(1-pentynyl)cyclohexane as a light pale yellow liquid.

(g) A solution of 4.5 g of 1,1-ethylenedioxy-4-(1-pentynyl)cyclohexanein 54 ml of tetrahydrofuran was treated dropwise with about 50 ml ofpre-condensed ammonia in a sulphonation flask provided with a magneticstirrer. The mixture was subsequently treated portionwise at -78° C.within 7 hours with 1.3 g of sodium. 1.5 hours after the last additionthe ammonia was removed by evaporation and the mixture was neutralizedwith 25% hydrochloric acid and left to stand overnight. The mixture wasthen partitioned three times in water/diethyl ether. The aqueous phaseswere back-extracted with diethyl ether. The organic phases were driedover magnesium sulphate and then freed from solvent on a rotaryevaporator. The resulting, pale yellow liquid (3.8 g) was treated with200 ml of acetone and 0.1 ml of concentrated sulphuric acid. The mixturewas heated to reflux for 10 minutes, then treated with water and freedfrom acetone on a rotary evaporator. The residue was partitioned threetimes in methylene chloride/water. The aqueous phases wereback-extracted with methylene chloride. The organic phases were driedover magnesium sulphate and evaporated. Chromatographic separation ofthe resulting, yellow liquid (3.5 g) on silica gel with ethylacetate/petroleum ether (vol. 7:93) gave 3.0 g (83.5%) of4-(trans-1-pentenyl)cyclohexanone as a pale yellow liquid.

(h) 1.63 g of 4-(trans-1-pentenyl)cyclohexanone were dissolved in 8 mlof diethyl ether and 14 ml of ethanol. Subsequently, the solution wastreated dropwise with about 70 ml of ammonia and portionwise withlithium wire until the colour of the mixture remained constant for 1.5hours (about 1.3 g of lithium). Thereafter, the ammonia was removed byevaporation and the mixture was made acid with ammonium chloride andhydrochloric acid and left to stand for 3 days. The mixture was thenpartitioned in diethyl ether/water and the aqueous phases wereback-extracted with diethyl ether. The organic phases were dried overmagnesium sulphate, filtered and freed from solvent on a rotaryevaporator. Low-pressure chromatography of the resulting, yellow oil onsilica gel with ethyl acetate/petroleum ether (vol. 10:90) gave 1.47 g(89.1%) of trans-4-(trans-1-pentenyl)cyclohexanol as a light-yellow,viscous oil.

The following compounds were manufactured in an analogous manner:

Trans-4-propylcyclohexanecarboxylic acidtrans-4-(trans-1-pentenyl)cyclohexyl ester; m.p. (C--S) 23.8° C., cl.p.(S--I) 50.7° C.,

trans-4-butylcyclohexanecarboxylic acidtrans-4-(trans-1-pentenyl)cyclohexyl ester; m.p. (C--S) 26.2° C., cl.p.(S--I) 65.0° C.

EXAMPLE 11

A mixture of 800 mg of trans-4-(trans-1-pentenyl)cyclohexanecarboxylicacid, 675.64 mg of p-ethoxyphenol, 1.01 g of dicyclohexylcarbodiimideand 49.79 mg of 4-(dimethylamino)pyridine was suspended in 14.5 ml ofmethylene chloride and stirred at room temperature for 20 hours. Themixture was subsequently diluted with diethyl ether, the precipitatedurea was filtered off and the filtrate was concentrated. The residue wastaken up in hexane and washed with dilute hydrochloric acid, sodiumhydrogen carbonate solution and water. The aqueous phases wereback-extracted twice with hexane. The organic phases were dried overmagnesium sulphate and evaporated. Low-pressure chromatography of theresulting residue on silica gel with ethyl acetate/petroleum ether (vol.3:97) gave 1.080 g (83.8%) oftrans-4-(trans-1-pentenyl)cyclohexanecarboxylic acid p-ethoxyphenylester. After recrystallization from 40 ml of hexane, there were finallyobtained 880 mg of product in the form of transparent crystals; m.p.(C--N) 57.2° C., cl.p. (N--I) 93.1° C.

The trans-4-(trans-1-pentenyl)cyclohexanecarboxylic acid used as thestarting material was prepared as follows:

(a) 7 g of methoxymethyl-triphenylphosphonium chloride were suspended in35 ml of t-butyl methyl ether and treated at -20° C. with 2.43 g ofpotassium t-butylate. The mixture was stirred at room temperature for 1hour, then treated dropwise at -20° C. with a solution of 2 g of4-(trans-1-pentenyl)cyclohexanone in 18 ml of tetrahydrofuran andstirred at room temperature for a further 1 hour. The mixture wassubsequently treated with water and extracted three times with 50 ml ofdiethyl ether each time. The extracts were washed with water and thewash-water was back-extracted with diethyl ether. The organic phaseswere dried over magnesium sulphate and freed from solvent. The residuewas dissolved in ethyl acetate and the solution was diluted withpetroleum ether, freed from precipitated triphenylphosphine oxide byfiltration and again concentrated. This procedure for the separation oftriphenylphosphine oxide was repeated a further twice and the resultingcrude product of 1-(methoxymethylene)-4-(trans-1-pentenyl)cyclohexanewas processed without additional purification.

(b) 2.75 g of 1-(methoxymethylene)-4-(trans-1-pentenyl)cyclohexane[crude product from paragraph (a)] were heated to reflux for 30 minuteswith 100 ml of tetrahydrofuran/2N hydrochloric acid (vol. 4:1) and thenstirred at room temperature overnight. The mixture was subsequentlytreated with 100 ml of water and extracted three times with 100 ml ofdiethyl ether each time. The extracts were washed with dilute sodiumhydrogen carbonate solution and water and the aqueous phases wereback-extracted with diethyl ether. The organic phases were dried overmagnesium sulphate and evaporated. Low-pressure chromatography of theresulting, yellowish liquid (2.5 g) on silica gel with petroleum etherand ethyl acetate/petroleum ether (vol. 3:97) gave 1.65 g (76%) of4-(trans-1-pentenyl)cyclohexanecarboxaldehyde.

(c) A solution of 1.6 g of 4-(trans-1-pentenyl)cyclohexanecarboxaldehydein 120 ml of acetone was cooled to -10° C., treated dropwise with 8Nchromic acid (about 10 ml) until the colour of the mixture remainedbrown-orange and stirred for 1 hour. Excess chromic acid was reduced bythe addition of isopropanol. The green solution was subsequentlypartitioned three times in water/methylene chloride. The organicextracts were washed twice with water and the wash-water wasback-extracted with methylene chloride. The organic phases were driedover magnesium sulphate and evaporated. The pale brown crystallineresidue (2.01 g) was dissolved partially in 20 ml of petroleum ether.Undissolved residue was filtered off and the filtrate was evaporated.Recrystallization of the resulting residue from 60 ml of petroleum etherat -78° C. gave 866 mg (49.5%) of4-(trans-1-pentenyl)cyclohexanecarboxylic acid as white crystals.

(d) A mixture of 1.29 g of 4-(trans-1-pentenyl)cyclohexanecarboxylicacid and 20 ml of a 11% (wt./vol.) solution of potassium hydroxide indiethylene glycol was boiled at reflux for 20 hours while gassing withargon. The mixture was subsequently made slightly acid with 25%hydrochloric acid and partitioned three times in water/methylenechloride. The organic extracts were washed twice with water and thewash-water was back-extracted with methylene chloride. The organicphases were dried over magnesium sulphate and freed from solvent on arotary evaporator. Recrystallization of the resulting, dark brown,crystallizing oil (1.17 g) from 50 ml of petroleum ether at -78° C. gave0.44 g of trans-4-(trans-1-pentenyl)cyclohexanecarboxylic acid as palebrown crystals. The mother liquor containing 0.695 g of crudecis/trans-4-(trans-1-pentenyl)cyclohexanecarboxylic acid was notworked-up.

EXAMPLE 12

A suspension of 6.64 g of methyltriphenylphosphonium bromide in 80 ml oft-butyl methyl ether was treated with 2.12 g of solid potassiumt-butylate at -10° C. within 3 minutes while gassing with argon in asulphonation flask provided with a mechanical stirrer. The mixture wasstirred at room temperature for a further 1 hour, then treated at 0° C.within 5 minutes with a solution of 3.0 g of3-[trans-4-(p-cyanophenyl)cyclohexyl]propionaldehyde in 20 ml of t-butylmethyl ether and stirred at room temperature for a further 15 minutes.The mixture was subsequently partitioned three times in diethylether/water. The organic extracts were washed twice with water, driedover magnesium sulphate, filtered and evaporated. In order to separatetriphenylphosphine oxide, the residue was dissolved in ethyl acetate andthe solution was diluted with petroleum ether, filtered and evaporated.Chromatographic separation of the resulting, pale brown oil (4.38 g) onsilica gel with ethyl acetate/petroleum ether (vol. 3:97) gave 2.83 g ofwhite crystals. Recrystallization from methanol and working-up of themother liquor finally gave a total of 2.116 g ofp-[trans-4-(3-butenyl)cyclohexyl]benzonitrile as white crystals; m.p.(C--N) 49.5° C., cl.p. (N--I) 52.5° C.

The 3-[trans-4-(p-cyclophenyl)cyclohexyl]propionaldehyde used as thestarting material was prepared as follows:

(a) A suspension of 29.0 g of methoxymethyl-triphenylphosphoniumchloride in 200 ml of t-butyl methyl ether was treated with 9.7 g ofpotassium t-butylate at -10° C. within 3 minutes while gassing withargon in a sulphonation flask provided with a mechanical stirrer. Theorange suspension was stirred at about 0° C. for 1 hour, then treateddropwise at -10° C. within 10 minutes with a solution of 12.0 g oftrans-4-(p-cyclophenyl)cyclohexanecarboxaldehyde in 90 ml of t-butylmethyl ether and stirred at 0° C. for a further 45 minutes. The mixturewas subsequently partitioned three times in diethyl ether/water. Theorganic extracts were washed twice with water, dried over magnesiumsulphate, filtered and evaporated. In order to separatetriphenylphosphine oxide, the residue was dissolved in ethyl acetate andthe solution was diluted with petroleum ether, filtered and evaporated.Chromatographic separation of the yellowish crystalline residue (16.3 g)on silica gel with ethyl acetate/petroleum ether (vol. 5:95) gave 10.1 g(74%) of p-[trans-4-(2-methoxyvinyl)cyclohexyl]benzonitrile as whitecrystals.

(b) A solution of 10.1 g ofp-[trans-4-(2-methoxyvinyl)cyclohexyl]benzonitrile in 200 ml oftetrahydrofuran/2N hydrochloric acid (vol. 4:1) was heated to reflux for1 hour while stirring. The mixture was subsequently partitioned threetimes in diethyl ether/water. The organic extracts were washed twicewith water, dried over magnesium sulphate, filtered and evaporated,there being obtained 9.8 g of2-[trans-4-(p-cyanophenyl)cyclohexyl]acetaldehyde as a light yellowish,crystalline residue.

(c) A suspension of 22.2 g of methoxymethyl-triphenylphosphoniumchloride in 150 ml of t-butyl methyl ether was treated with 7.4 g ofsolid potassium t-butylate at 0° C. within 3 minutes while gassing withargon in a sulphonation flask provided with a mechanical stirrer. Theorange suspension was stirred at 0° C. for 1 hour and then treateddropwise within 10 minutes with a solution of 9.8 g of2-[trans-4-(p-cyanophenyl)cyclohexyl]acetaldehyde in 100 ml oftetrahydrofuran. Subsequently, the suspension was left to warm slowly toroom temperature while stirring. After 15 hours, the suspension waspartitioned three times in diethyl ether/water. The organic extractswere washed twice with water, dried over magnesium sulphate, filteredand evaporated. In order to separate triphenylphosphine oxide, theresidue was dissolved in ethyl acetate and the solution was diluted withpetroleum ether, filtered and evaporated. Chromatographic separation ofthe resulting, yellowish oil (13.7 g) on silica gel with ethylacetate/petroleum ether (vol. 5:95) gave 10.5 g (96%) ofp-[trans-4-(3-methoxy-2-propenyl)cyclohexyl]benzonitrile as a colourlessoil.

(d) A solution of 10.5 g ofp-[trans-4-(3-methoxy-2-propenyl)cyclohexyl]benzonitrile in 200 ml oftetrahydrofuran/2N hydrochloric acid (vol. 4:1) was heated to reflux for45 minutes while stirring. The mixture was then partitioned three timesin diethyl ether/water. The organic extracts were washed twice withwater, dried over magnesium sulphate, filtered and evaporated.Chromatographic separation of the white, crystalline residue (9.9 g) onsilica gel with ethyl acetate/petroleum ether (vol. 10:90 and 30:70)finally gave 9.4 g (95%) of3-[trans-4-(p-cyanophenyl)cyclohexyl]propionaldehyde as white crystals.

EXAMPLE 13

A solution of 9.54 g ofp-[trans-4-(erythro-3,4-dibromopentyl)cyclohexyl]benzonitrile in 100 mlof glacial acetic acid was treated with 9.8 g of zinc powder whilegassing with argon in a round flask provided with a magnetic stirrer.The mixture was stirred at room temperature for 30 minutes and thenpartitioned three times in petroleum ether/water. The organic extractswere washed twice with water, dried over magnesium sulphate, filteredand concentrated. Chromatographic separation of the oily residue (5.56g) on silica gel coated with silver nitrate (prepared by suspending 300g of silica gel in 500 ml of a 0.2M solution of silver nitrate inacetonitrile, subsequently filtering and drying the residue) usingdiethyl ether/hexane (vol. 1:9) as the eluent gave 3.2 g of crudeproduct as white crystals. After recrystallization from 80 ml ofmethanol, 1.65 g (28%) ofp-[trans-4-(trans-3-pentenyl)cyclohexyl]benzonitrile were obtained aswhite crystals. The mother liquor and the impure fractions from thechromatographic separation were combined and again purified on silicagel coated with silver nitrate using diethyl ether/hexane (vol. 1:9) asthe eluent. Recrystallization of the resulting, crystalline product (1.5g) from 40 ml of methanol gave a further 0.65 g ofp-[trans-4-(trans-3-pentenyl)cyclohexyl]benzonitrile as white crystals;m.p. (C--N) 59.8° C., cl.p. (N--I) 73.7° C.

The p-[trans-4-(erythro-3,4-dibromopentyl)cyclohexyl]benzonitrile usedas the starting material was prepared as follows:

(a) A suspension of 14.8 g of ethyltriphenylphosphonium bromide in 150ml of t-butyl methyl ether was treated with 4.54 g of solid potassiumt-butylate at -10° C. within 5 minutes while gassing with argon in asulphonation flask provided with a mechanical stirrer. The suspensionwas stirred at room temperature for 1 hour, then treated dropwise at 0°C. within 5 minutes with a solution of 6.4 g of3-[trans-4-(p-cyanophenyl)cyclohexyl]propionaldehyde in 40 ml of t-butylmethyl ether and stirred at room temperature for a further 15 hours. Themixture was subsequently partitioned three times in diethyl ether/water.The organic extracts were washed twice with water, dried over magnesiumsulphate, filtered and concentrated. In order to separatetriphenylphosphine oxide, the residue was dissolved in ethyl acetate andthe solution was diluted with petroleum ether, filtered andconcentrated. Chromatographic separation of the resulting, yellowish oil(8.55 g) on silica gel with ethyl acetate/petroleum ether (vol. 3:97)gave 5.93 g (89%) of p-[trans-4-(3-pentenyl)cyclohexyl]benzonitrile aswhite crystals.

(b) A solution of 4.49 g of 90% m-chloroperbenzoic acid in 100 ml ofmethylene chloride was treated with 11.3 g of powdered potassiumcarbonate. The mixture was treated dropwise at 0° C. within 5 minuteswith a solution of 5.93 g ofp-[trans-4-(3-pentenyl)cyclohexyl]benzonitrile in 20 ml of methylenechloride and stirred at room temperature for 2 hours. The mixture wassubsequently treated with a further 4.49 g of 90% m-chloroperbenzoicacid and the resulting mixture was stirred further. After a total of 70hours, the mixture was partitioned three times in methylene chloride/10%sodium thiosulphate solution. The organic extracts were washed withsodium thiosulphate solution and water, dried over magnesium sulphate,filtered and concentrated. Chromatographic separation of the resulting,light yellowish oil (6.3 g) on silica gel with ethyl acetate/petroleumether (vol. 10:90) gave 6.27 g (99.5%) ofp-[trans-4-(3,4-epoxypentyl)cyclohexyl]benzonitrile as a colourless oil.

(c) A solution of 7.4 g of triphenylphosphine in 80 ml of methylenechloride was treated dropwise with a solution of 1.5 ml of bromine in 20ml of methylene chloride while gassing with argon until the yellowcolour remained. The mixture was then evaporated on a rotary evaporatorand the residue was dried in a high vacuum for 1 hour. The yellow,crystalline residue was suspended in 120 ml of benzene. The suspensionwas treated with 6.27 g ofp-[trans-4-(3,4-epoxypentyl)cyclohexyl]benzonitrile and heated to refluxwhile stirring for 1 hour. The mixture was subsequently filtered onsilica gel using toluene as the eluent. Concentration of theproduct-containing fractions finally gave 9.54 g (99.1%) ofp-[trans-4-(erythro-3,4-dibromopentyl)cyclohexyl]benzonitrile as a lightbrownish oil.

EXAMPLE 14

A solution of methylmagnesium iodide in diethyl ether (prepared from 384mg of magnesium shavings and 0.984 ml of methyl iodide in 30 ml ofdiethyl ether) was treated dropwise at room temperature with a solutionof 2.0 g of p-[trans-4-(trans-1-pentenyl)cyclohexyl]benzonitrile. Themixture was heated to reflux for 15 minutes. 30 ml of toluene weresubsequently added to the mixture, the diethyl ether was distilled offand the resulting mixture was heated to reflux for a further 1.5 hours.The mixture was then treated cautiously at 0° C. with saturated ammoniumchloride solution and partitioned three times in diethyl ether/water.The organic extracts were washed twice with water, dried over magnesiumsulphate, filtered and evaporated. Chromatographic separation of theyellow, crystalline residue (2.6 g) on silica gel with ethylacetate/petroleum ether (vol. 5:95) gave 1.85 g (87%) ofp-[trans-4-(trans-1-pentenyl)cyclohexyl]acetophenone as light yellowcrystals.

EXAMPLE 15

A solution of 1.35 g ofp-[trans-4-(trans-1-pentenyl)cyclohexyl]acetophenone in 16 ml of ethanoland 16 ml of diethylene glycol was treated with 0.486 ml of hydrazinehydrate while gassing with argon and then heated to reflux (bathtemperature 110° C.) while stirring for 1.5 hours. The mixture wassubsequently treated with 550 mg of solid potassium hydroxide, the bathtemperature was increased to 210° C. and the ethanol was distilled off.After 2.5 hours at 210° C., the reaction was interrupted and the mixturewas partitioned three times in water/petroleum ether. The organicextracts were washed twice with water, dried over magnesium sulphate andevaporated. Chromatographic separation of the residue (1.23 g) on silicagel with hexane as the eluent gave 1.16 g (91%) of4-ethyl-1-[trans-4-(trans-1-pentenyl)cyclohexyl]benzene as a colourlessoil; m.p. (C--I) -3.1° C.

The following compounds were manufactured in an analogous manner:

4-Propyl-1-[trans-4-(trans-1-pentenyl)cyclohexyl]benzene; m.p. (C--I)7.0° C.,

4-ethyl-1-[2-(trans-4-(trans-1-propenyl)cyclohexyl)ethyl]benzene; m.p.(C--I) 1.7° C., cl.p. -26° C.

EXAMPLE 16

A suspension of 404.4 mg of diphosphorus tetraiodide in 5 ml ofmethylene chloride was treated dropwise while gassing with argon at roomtemperature within 5 minutes with a solution of 205 mg of4-ethoxy-1-[trans-4-(1,2-epoxypentyl)cyclohexyl]benzene and 0.703 ml ofpyridine in 8 ml of methylene chloride. The suspension was heated toreflux while stirring, a further 404.4 mg of diphosphorus tetraiodidebeing added after 2 hours. After stirring under reflux for a total of 19hours, the reaction was interrupted and the mixture was treated with 1Nhydrochloric acid and extracted three times with diethyl ether. Theorganic extracts were washed successively with 1N hydrochloric acid,sodium thiosulphate solution and water, dried over magnesium sulphate,filtered and evaporated. Chromatographic separation of the residue (0.2g) on silica gel with ethyl acetate/petroleum ether (vol. 3:97) as theeluent gave 120 mg of4-ethoxy-1-[trans-4-(trans-1-pentenyl)cyclohexyl]benzene. Afterrecrystallization from 10 ml of methanol, the product was obtained aswhite crystals of melting point (C--N) 32.2° C. and clearing point(N--I) 54.9° C.

The 4-ethoxy-1-[trans-4-(1,2-epoxypentyl)cyclohexyl]benzene used as thestarting material was prepared as follows:

(a) A solution of 2.63 g ofp-[trans-4-(trans-1-pentenyl)cyclohexyl]acetophenone in 90 ml ofmethylene chloride was treated successively with 7.46 g ofm-chloroperbenzoic acid and 100 mg of 2,6-di(t-butyl)-p-cresol at 0° C.while gassing with argon. The mixture was stirred at room temperaturefor 40 hours with the exclusion of light. The mixture was subsequentlypartitioned in methylene chloride/10% sodium thiosulphate solution andthe organic phase was washed once with 10% sodium thiosulphate solutionand twice with sodium hydrogen carbonate solution. The aqueous phaseswere back-extracted three times with methylene chloride. The combinedorganic phases were dried over magnesium sulphate, filtered andevaporated. The yellow, oily residue of4-acetoxy-1-[trans-4-(1,2-epoxypentyl)cyclohexyl]benzene was dissolvedin 100 ml of 1N methanolic potassium hydroxide solution and stirred atroom temperature for 1 hour. The mixture was subsequently adjusted toabout pH 8 with 10 ml of 25% hydrochloric acid and partitioned indiethyl ether/water. The aqueous phase was extracted three times withdiethyl ether. The organic phases were dried over magnesium sulphate,filtered and evaporated. Chromatographic separation of the resulting,brown oil (2.96 g) on silica gel with ethyl acetate/petroleum ether(vol. 10:90) gave 2.16 g ofp-[trans-4-(1,2-epoxypentyl)cyclohexyl]phenol as yellowish crystals.

(b) A solution of 1.6 g of p-[trans-4-(1,2-epoxypentyl)cyclohexyl]phenolin 120 ml of acetone was treated with 1.89 ml of ethyl iodide and 3.24 gof powdered potassium carbonate while gassing with argon. The mixturewas heated to reflux while stirring for 24 hours, then evaporated on arotary evaporator and the residue was partitioned in diethylether/water. The aqueous phase was extracted three times with diethylether. The organic phases were washed twice with water, dried overmagnesium sulphate, filtered and evaporated. Chromatographic separationof the resulting, yellowish oil (1.76 g) on silica gel with ethylacetate/petroleum ether (vol. 5:95) gave 1.45 g (82%) of4-ethoxy-1-[trans-4-(1,2-epoxypentyl)cyclohexyl]benzene as an oilyliquid.

EXAMPLE 17

A mixture of 1.00 g of 2-(trans-1-pentenyl)-1,3-propanediol, 1.11 g ofp-butoxybenzaldehyde, 3 drops of 2N sulphuric acid and 40 ml of toluenewas heated to reflux for 2 hours with separation of water. The mixturewas subsequently treated with 7 drops of triethylamine, left to cool,washed with 5 ml of saturated sodium hydrogen carbonate solution andthree times with 10 ml of water each time, dried over sodium carbonate,filtered and concentrated. The semi-crystalline residue (1.86 g) waschromatographed on silica gel with hexane/diethyl ether (vol. 97:3). Theproduct-containing fractions were pooled (0.99 g) and recrystallizedtwice from hexane at -25° C. There was obtained 0.44 g of puretrans-2-(p-butoxyphenyl)-5-(trans-1-pentenyl)-m-dioxane; m.p. (C--N)60.6° C., cl.p. (N--I) 61.9° C.

The 2-(trans-1-pentenyl)-1,3-propanediol used as the starting materialwas prepared as follows:

A solution of 16.1 g of diethyl 2-(trans-1-pentenyl)malonate(Tetrahedron Lett. 1979, 861) in 75 ml of tetrahydrofuran was addeddropwise to a suspension of 5.3 g of lithium aluminium hydride in 200 mlof dry tetrahydrofuran at 5° C. within 1 hour while stirring in an inertgas atmosphere. The mixture was stirred at room temperature for afurther 3.5 hours and then successively treated dropwise with 15 ml ofacetone and 20 ml of saturated sodium hydrogen carbonate solution. Themixture was filtered, the filtrate was concentrated and the residue (8.2g) was distilled in a bulb-tube at 150° C./about 1 Torr. There were thusobtained 6.5 g of 2-(trans-1-pentenyl)-1,3-propanediol as a colourlessoil.

The following compounds were manufactured in an analogous manner:

p-[Trans-5-(trans-1-propenyl)-m-dioxan-2-yl]benzonitrile; m.p. (C--I)97° C., cl.p. (N--I) 73° C.,

p-[trans-5-(trans-1-butenyl)-m-dioxan-2-yl]benzonitrile; m.p. (C--I)92.2° C.,

p-[trans-5-(trans-1-pentenyl)-m-dioxan-2-yl]benzonitrile; m.p. (C--I)67.2° C., cl.p. (N--I) 59.1° C.,

p-[trans-5-(trans-1-hexenyl)-m-dioxan-2-yl]benzonitrile; m.p. (C--I)50.5° C., cl.p. (N--I) 37.0° C.,

p-[trans-5-(trans-1-heptenyl)-m-dioxan-2-yl]benzonitrile; m.p. (C--I)49.3° C., cl.p. (N--I) 49.2° C.,

trans-2-(p-ethoxyphenyl)-5-(trans-1-pentenyl)-m-dioxane; m.p. (C--I)66.3° C., cl.p. (N--I) 64.4° C.,

trans-2-(p-ethoxyphenyl)-5-(trans-1-hexenyl)-m-dioxane; m.p. (C--I)56.7° C., cl.p. (N--I) 47.5° C.,

trans-2-(p-butoxyphenyl)-5-(trans-1-propenyl)-m-dioxane; m.p. (C--N)59.5° C., cl.p. (N--I) 61.2° C.,

trans-2-(p-butoxyphenyl)-5-(trans-1-hexenyl)-m-dioxane; m.p. (C--N)30.5° C., S_(B) --N 30.3° C., cl.p. (N--I) 48.4° C.,

trans-2-(p-propylphenyl)-5-(trans-1-propenyl)-m-dioxane; m.p. (C--I)57.8° C.,

trans-2-(p-propylphenyl)-5-(trans-1-pentenyl)-m-dioxane; m.p. (C--I)45.2° C., cl.p. (S_(B) --I) 35.3° C.,

trans-2-(trans-4-butylcyclohexyl)-5-(trans-1-propenyl)-m-dioxane; m.p.(C--N) 47.3° C., cl.p. (N--I) 48.4° C.,

trans-2-(trans-4-propylcyclohexyl)-5-(trans-1-pentenyl)-m-dioxane; m.p.(C--S_(B)) 31.2° C., cl.p. (S_(B) --I) 85.7° C.

EXAMPLE 18

A mixture of 2.00 g of trans-4-cyanocyclohexanecarboxaldehyde, 2.13 g of2-pentyl-1,3-propanediol and 65 mg of p-toluenesulphonic acid in 100 mlof benzene was heated to reflux for 3 hours while gassing with argon andwith separation of water in a round flask provided with a waterseparator and a reflux condenser. The mixture was subsequently treatedwith 3.0 g of potassium carbonate, stirred at room temperature for 16hours, then filtered and the filtrate was concentrated.Recrystallization of the crystalline residue (4.1 g) from hexane at 0°C. gave 1.47 g (38%) oftrans-4-(trans-5-pentyl-m-dioxan-2-yl)cyclohexanecarbonitrile ascolourless crystals in a purity of 99.1%. After a furtherrecrystallization from hexane at 0° C., the purity increased to 99.9%;m.p. (C--N) 45.6° C., cl.p. (N--I) 46.7° C.

The following compounds were manufactured in an analogous manner:

Trans-4-(trans-5-propyl-m-dioxan-2-yl)cyclohexanecarbonitrile; m.p.(C--I) 63.6° C., cl.p. (N--I) 39.3° C.,

trans-4-(trans-5-butyl-m-dioxan-2-yl)cyclohexanecarbonitrile, m.p.(C--N) 33.2° C., cl.p. 35.6° C.,

trans-4-(trans-5-heptyl-m-dioxan-2-yl)cyclohexanecarbonitrile, m.p.(C--I) 56.3° C., cl.p. (N--I) 45.0° C.

I claim:
 1. A compound of the formula: ##STR22## wherein R¹ is hydrogenor straight-chain alkyl; R² is --CN, --R, --COR, --COOR or when R² ispositioned on an aromatic ring R² also can be --OR, --OOCR or --F; R isalkyl; A is a group with 1 to 4 six-membered rings, A and B rings beinglinked directly with one another, and rings A in each case being linkedvia a single covalent bond or being linked at one or two positions alsovia --COO--, --OOC-- or --CH₂ CH₂ --; the six-membered rings in A andring B each are 1,4-phenylene or trans-1,4-cyclohexylene, with theproviso that a maximum of two adjacent trans-1,4-cyclohexylene rings arelinked directly via a single covalent bond; and m is the integer 2, orwhen ring B is trans-1,4-cyclohexylene, m also can be the integer
 0. 2.The compound of the claim 1, wherein the compound has the formula:##STR23## wherein rings B, C and D each are 1,4-phenylene ortrans-1,4-cyclohexylene X¹ is a single covalent bond and X² is --COO--,--OOC--, --CH₂ CH₂ --, or when at least one of the rings B, C and D isnot trans-1,4-cyclohexylene, X² also can be a single covalent bond; n isthe integer 0 or 1; and R¹, R², R and m have the significances given inclaim
 1. 3. The compound of claim 1, wherein ring B istrans-1,4-cyclohexylene.
 4. The compound of claim 1, wherein thecompound has the formula: ##STR24## wherein each of rings B¹ and B² is1,4-phenylene or trans-1,4-cyclohexylene; X¹ is a single covalent bondand X² is --COO--, --OOC--, --CH₂ CH₂ --, or when at least one of therings B¹ and B² is not trans-1,4-cyclohexylene, X² also can be a singlecovalent bond; n is the integer 0 or 1; and R¹, R², R and m have thesignificances given in claim
 1. 5. The compound of claim 4, wherein X¹is a single covalent bond; X² is a single covalent bond; and each ofrings B¹ and B² is 1,4-phenylene.
 6. The compound of claim 2, wherein nis the integer
 0. 7. The compound of claim 1, wherein R isstraight-chain C₁ -C₁₂ -alkyl.
 8. The compound of claim 1, wherein R² iscyano, alkyl, or when R² is positioned on an aromatic ring R² also canbe alkoxy.
 9. The compound of claim 8, wherein R² is cyano, C₃ -C₇-alkyl, or when R² is positioned on an aromatic ring R² also can be C₂-C₆ -alkoxy.
 10. The compound of claim 1, wherein R¹ is hydrogen orstraight-chain C₁ -C₁₀ -alkyl, and m is the integer
 0. 11. The compoundof claim 1, wherein R¹ is hydrogen or straight-chain C₁ -C₈ -alkyl, m isthe integer
 2. 12. The compound of claim 10, wherein R¹ is hydrogen orstraight-chain C₁ -C₅ -alkyl, and m is the integer
 0. 13. The compoundof claim 11, wherein R¹ is hydrogen or straight-chain C₁ -C₃ -alkyl, andm is the integer
 2. 14. The compound of claim 1, wherein the compoundhas the formula: ##STR25## wherein each of rings B¹, B², B³ and B⁴ is1,4-phenylene or trans-1,4-cyclohexylene; n is the integer 0 or 1; X¹ isa single covalent bond and each of X², X³ and X⁴ is a single covalentbond, --COO--, --OOC-- or --CH₂ CH₂ --, with the proviso that a maximumof two adjacent trans-1,4-cyclohexylene rings are linked directly via asingle covalent bond; and R¹, R², R and m have the significances givenin claim
 1. 15. The compound of claim 14, wherein m is the integer 0.16. A liquid crystalline mixture comprising at least two components,wherein at least one component is a compound of the formula: ##STR26##wherein R¹ is hydrogen or straight-chain alkyl; R² is --CN, --R, --COR,--COOR or when R² is positioned on an aromatic ring R² also can be --OR,--OOCR or --F; R is alkyl; A is a group with 1 to 4 six-membered rings,A and B rings being linked directly with one another, and with rings Ain each case being linked via a single covalent bond or being linked atone or two positions also via --COO--, --OOC-- or --CH₂ CH₂ --; thesix-membered rings in A and ring B each are 1,4-phenylene ortrans-1,4-cyclohexylene, with the proviso that a maximum of two adjacenttrans-1,4-cyclohexylene rings are linked directly via a single covalentbond; and m is the integer 2, or when ring B is trans-1,4-cyclohexylene,m also can be the integer
 0. 17. The liquid crystalline mixture of claim16, wherein the other component is one or more compounds selected fromthe group consisting of: ##STR27## wherein ring B¹ is 1,4-phenylene ortrans-1,4-cyclohexylene; R⁹ is straight-chain C₂ -C₇ -alkyl; R¹⁰ iscyano or straight-chain C₁ -C₆ -alkoxy, R¹¹ is cyano, straight-chain C₁-C₇ -alkyl or C₁ -C₇ -alkoxy; each of R¹² and R¹³ is straight-chain C₁-C₇ -alkyl; p is the integer 0 or 1; R¹⁴ is trans-4-alkylcyclohexyl,4'-alkyl-4-biphenylyl, p-(trans-4-alkylcyclohexyl)phenyl,2-(trans-4-alkylcyclohexyl)ethyl orp-[2-(trans-4-alkylcyclohexyl)ethyl]phenyl and R¹⁵ istrans-4-alkylcyclohexyl; or R¹⁴ is trans-4-alkylcyclohexyl and R¹⁵ isp-(trans-4-alkylcyclohexyl)phenyl,p-[2-(trans-4-alkylcyclohexyl)ethyl]phenyl or4'-(trans-4-alkyl-cyclohexyl)-4-biphenylyl; or R¹⁴ is p-alkylphenyl andR¹⁵ is p-[2-(trans-4-alkylcyclohexyl)ethyl]phenyl; each of the alkylgroups in R¹⁴ and R¹⁵ is straight-chain C₁ -C₇ -alkyl; one of Z¹ and Z²is --COO-- or --OOC-- and the other as well as each of Z³ and Z⁴ aresingle covalent bonds or one of Z¹, Z², Z³ and Z⁴ also can be --CH₂ CH₂--; each of rings B¹ and B⁵ in formula XCI is a group of the formula##STR28## or trans-1,4-cyclohexylene; each of rings B², B³ and B⁴ is agroup of formula XCII, or when rings B², B³ and B⁴ are not linked withat least one of the other two of these rings by a single covalent bond,rings B², B³ and B⁴ also can be trans-1,4-cyclohexylene; Y is hydrogenor when Y is positioned on one of the rings of formula XCII which is notlinked with a further ring via a single covalent bond, Y also can befluorine, chlorine or methyl; each of R¹⁶ and R¹⁷ is straight-chain C₁-C₇ -alkyl or when positioned on a ring of formula XCII R¹⁶ and R¹⁷ alsocan be straight-chain C₁ -C₇ -alkoxy.
 18. The liquid crystalline mixtureof claim 16, wherein the other component is a compound of the formula:##STR29## wherein R⁸ is straight-chain C₁ -C₁₂ alkyl.
 19. Anelectro-optical cell comprising:(a) two plate means; (b) liquid crystalmeans disposed between the two plate means and including a compound ofthe formula: ##STR30## wherein R¹ is hydrogen or straight-chain alkyl;R² is --CN, --R, --COR, --COOR or when R² is positioned on an aromaticring R² also can be --OR, --OOCR or --F; R is alkyl; A is a group with 1to 4 six-membered rings, A and B rings being linked directly with oneanother, and rings A in each case being linked via a single covalentbond or being linked at one or two positions also via --COO--, --OOC--or --CH₂ CH₂ --; the six-membered rings in A and ring B each are1,4-phenylene or trans-1,4-cyclohexylene, with the proviso that amaximum of two adjacent trans-1,4-cyclohexylene rings are linkeddirectly via a single covalent bond; and m is the integer 2, or whenring B is trans-1,4-cyclohexylene, m also can be the integer 0; and (c)means for applying an electrical potential to said plate means.
 20. Thecompound of claim 1,p-[trans-4-(trans-1-propenyl)cyclohexyl]benzonitrile.
 21. The compoundof claim 1, p-[trans-4-(trans-1-butenyl)cyclohexyl]benzonitrile.
 22. Thecompound of claim 1,p-[trans-4-(trans-1-pentenyl)cyclohexyl]benzonitrile.
 23. The compoundof claim 1, p-[trans-4-(3-butenyl)cyclohexyl]benzonitrile.
 24. Thecompound of claim 1,p-[trans-4-(trans-3-pentenyl)cyclohexyl]benzonitrile.